High Performance, 145 MHz
FastFET Op Amps
AD8065/AD8066
Rev. J
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FEATURES
Qualified for automotive applications
FET input amplifier
1 pA input bias current
Low cost
High speed: 145 MHz, −3 dB bandwidth (G = +1)
180 V/μs slew rate (G = +2)
Low noise
7 nV/√Hz (f = 10 kHz)
0.6 fA/√Hz (f = 10 kHz)
Wide supply voltage range: 5 V to 24 V
Single-supply and rail-to-rail output
Low offset voltage 1.5 mV maximum
High common-mode rejection ratio: −100 dB
Excellent distortion specifications
SFDR −88 dBc @ 1 MHz
Low power: 6.4 mA/amplifier typical supply current
No phase reversal
Small packaging: SOIC-8, SOT-23-5, and MSOP-8
APPLICATIONS
Automotive driver assistance systems
Photodiode preamps
Filters
A/D drivers
Level shifting
Buffering
CONNECTION DIAGRAMS
1
2
3
5
4
1
4
3
5
27
8
6
8
7
6
5
1
2
3
4
V
OUT
V
OUT1
V
OUT2
V
OUT
–V
S
–V
S
–V
S
+IN
+V
S
+V
S
+V
S
–IN
–IN1
+IN1 –IN2
+IN2
NC
–IN
+IN
NC
NC
TOP VIEW
(Not to Scale)
TOP VIEW
(Not to Scale)
TOP VIEW
(Not to Scale)
AD8065
AD8066
AD8065
02916-E-001
Figure 1.
GENERAL DESCRIPTION
The AD8065/AD80661 FastFET™ amplifiers are voltage feedback
amplifiers with FET inputs offering high performance and ease
of use. The AD8065 is a single amplifier, and the AD8066 is a
dual amplifier. These amplifiers are developed in the Analog
Devices, Inc. proprietary XFCB process and allow exceptionally
low noise operation (7.0 nV/√Hz and 0.6 fA/√Hz) as well as
very high input impedance.
With a wide supply voltage range from 5 V to 24 V, the ability to
operate on single supplies, and a bandwidth of 145 MHz, the
AD8065/AD8066 are designed to work in a variety of applications.
For added versatility, the amplifiers also contain rail-to-rail outputs.
Despite the low cost, the amplifiers provide excellent overall
performance. The differential gain and phase errors of 0.02%
and 0.02°, respectively, along with 0.1 dB flatness out to 7 MHz,
make these amplifiers ideal for video applications. Additionally,
they offer a high slew rate of 180 V/μs, excellent distortion (SFDR
of −88 dBc @ 1 MHz), extremely high common-mode rejection
of −100 dB, and a low input offset voltage of 1.5 mV maximum
under warmed up conditions. The AD8065/AD8066 operate
using only a 6.4 mA/amplifier typical supply current and are
capable of delivering up to 30 mA of load current.
The AD8065/AD8066 are high performance, high speed, FET
input amplifiers available in small packages: SOIC-8, MSOP-8,
and SOT-23-5. They are rated to work over the industrial
temperature range of −40°C to +85°C.
The AD8065WARTZ-REEL7 is fully qualified for automotive
applications. It is rated to operate over the extended temperature
range (−40°C to +105°C), up to a maximum supply voltage
range of +5V only.
–6
–3
0
3
6
9
12
15
18
21
24
GAIN (dB)
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-002
G = +10 V
O
= 200mV p-p
G = +5
G = +2
G = +1
Figure 2. Small Signal Frequency Response
1 Protected by U. S. Patent No. 6,262,633.
AD8065/AD8066
Rev. J | Page 2 of 28
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Connection Diagrams ...................................................................... 1
General Description ......................................................................... 1
Revision History ............................................................................... 3
Specifications ±5 V ........................................................................... 4
Specifications ±12 V ......................................................................... 6
Specifications +5 V ........................................................................... 7
Absolute Maximum Ratings ............................................................ 9
Maximum Power Dissipation ..................................................... 9
Output Short Circuit .................................................................... 9
ESD Caution .................................................................................. 9
Typical Performance Characteristics ........................................... 10
Test Circuits ..................................................................................... 17
Theory of Operation ...................................................................... 20
Closed-Loop Frequency Response ........................................... 20
Noninverting Closed-Loop Frequency Response .................. 20
Inverting Closed-Loop Frequency Response ......................... 20
Wideband Operation ................................................................. 21
Input Protection ......................................................................... 21
Thermal Considerations ............................................................ 22
Input and Output Overload Behavior ..................................... 22
Layout, Grounding, and Bypassing Considerations .................. 23
Power Supply Bypassing ............................................................ 23
Grounding ................................................................................... 23
Leakage Currents ........................................................................ 23
Input Capacitance ...................................................................... 23
Output Capacitance ................................................................... 23
Input-to-Output Coupling ........................................................ 24
Wideband Photodiode Preamp ................................................ 24
High Speed JFET Input Instrumentation Amplifier.............. 25
Video Buffer ................................................................................ 26
Outline Dimensions ....................................................................... 27
Ordering Guide .......................................................................... 28
Automotive Products ................................................................. 28
AD8065/AD8066
Rev. J | Page 3 of 28
REVISION HISTORY
8/10—Rev. I to Rev. J
Changes to Features Section, Applications Section, and General
Description Section ........................................................................... 1
Change to Table 1 .............................................................................. 4
Change to Table 3 .............................................................................. 7
Changes to Table 4 ............................................................................ 9
Changes to Figure 9 ......................................................................... 10
Changes to Inverting Closed-Loop Frequency Response
Section .............................................................................................. 20
Moved Leakage Currents Section, Input Capacitance Section,
and Output Capacitance Section ................................................... 23
Moved Input-to-Input Coupling Section, Wideband
Photodiode Preamp Section, and Figure 59 ................................ 24
Changes to Table 5 .......................................................................... 25
Moved Figure 60 and High Speed JFET Input Instrumentation
Amplifier Section ............................................................................ 25
Updated Outline Dimensions ........................................................ 27
Changes to Ordering Guide ........................................................... 28
Added Automotive Products Section ........................................... 28
3/09—Rev. H to Rev. I
Changes to High Speed JFET Input Instrumentation Amplifier
Section .............................................................................................. 23
Updated Outline Dimensions ........................................................ 24
9/08—Rev. G to Rev. H
Deleted Usable Range Parameter, Table 1 ...................................... 3
Deleted Usable Range Parameter, Table 2 ...................................... 4
Deleted Usable Range Parameter, Table 3 ...................................... 5
Changes to Layout ............................................................................. 6
Changes to Input and Output Overload Behavior Section ........ 19
Changes to Table 5 Expressions Column ..................................... 22
1/06—Rev. F to Rev. G
Changes to Ordering Guide ........................................................... 26
12/05—Rev. E to Rev. F
Updated Format ................................................................. Universal
Changes to Features .......................................................................... 1
Changes to General Description ..................................................... 1
Changes to Figure 22 through Figure 27 ...................................... 11
Updated Outline Dimensions ........................................................ 25
Changes to Ordering Guide ........................................................... 26
2/04—Rev. D to Rev. E.
Updated Format ................................................................ Universal
Updated Figure 56 ......................................................................... 21
Updated Outline Dimensions ...................................................... 25
Updated Ordering Guide ............................................................. 26
11/03—Rev. C to Rev. D.
Changes to Features ......................................................................... 1
Changes to Connection Diagrams ................................................. 1
Updated Ordering Guide ................................................................ 5
Updated Outline Dimensions ...................................................... 22
4/03—Rev. B to Rev. C.
Added SOIC-8 (R) for the AD8065 ............................................... 4
2/03—Rev. A to Rev. B.
Changes to Absolute Maximum Ratings....................................... 4
Changes to Test Circuit 10 ........................................................... 14
Changes to Test Circuit 11 ........................................................... 15
Changes to Noninverting Closed-Loop Frequency Response 16
Changes to Inverting Closed-Loop Frequency Response ....... 16
Updated Figure 6 .......................................................................... 18
Changes to Figure 7 ...................................................................... 19
Changes to Figure 10 .................................................................... 21
Changes to Figure 11 .................................................................... 22
Changes to High Speed JFET Instrumentation Amplifier ...... 22
Changes to Video Buffer .............................................................. 22
8/02—Rev. 0 to Rev. A.
Added AD8066 .................................................................. Universal
Added SOIC-8 (R) and MSOP-8 (RM) ......................................... 1
Edits to General Description .......................................................... 1
Edits to Specifications ...................................................................... 2
New Figure 2 ..................................................................................... 5
Changes to Ordering Guide ............................................................ 5
Edits to TPCs 18, 25, and 28 ........................................................... 8
New TPC 36 ................................................................................... 11
Added Test Circuits 10 and 11 .................................................... 14
MSOP (RM-8) Added .................................................................. 23
AD8065/AD8066
Rev. J | Page 4 of 28
SPECIFICATIONS ±5 V
@ TA = 25°C, VS = ±5 V, RL = 1 kΩ, unless otherwise noted.
Table 1.
Parameter Conditions Min Typ Max Unit
DYNAMIC PERFORMANCE
−3 dB Bandwidth G = +1, VO = 0.2 V p-p (AD8065) 100 145 MHz
AD8065WARTZ only: TMIN − TMAX 88 MHz
G = +1, VO = 0.2 V p-p (AD8066) 100 120 MHz
G = +2, VO = 0.2 V p-p 50 MHz
G = +2, VO = 2 V p-p 42 MHz
Bandwidth for 0.1 dB Flatness G = +2, VO = 0.2 V p-p 7 MHz
Input Overdrive Recovery Time G = +1, −5.5 V to +5.5 V 175 ns
Output Recovery Time G = −1, −5.5 V to +5.5 V 170 ns
Slew Rate G = +2, VO = 4 V step 130 180 V/μs
AD8065WARTZ only: TMIN − TMAX 155 V/μs
Settling Time to 0.1% G = +2, VO = 2 V step 55 ns
G = +2, VO = 8 V step 205 ns
NOISE/HARMONIC PERFORMANCE
SFDR fC = 1 MHz, G = +2, VO = 2 V p-p −88 dBc
f
C = 5 MHz, G = +2, VO = 2 V p-p −67 dBc
f
C = 1 MHz, G = +2, VO = 8 V p-p −73 dBc
Third-Order Intercept fC = 10 MHz, RL = 100 Ω 24 dBm
Input Voltage Noise f = 10 kHz 7 nV/√Hz
Input Current Noise f = 10 kHz 0.6 fA/√Hz
Differential Gain Error NTSC, G = +2, RL = 150 Ω 0.02 %
Differential Phase Error NTSC, G = +2, RL = 150 Ω 0.02 Degrees
DC PERFORMANCE
Input Offset Voltage VCM = 0 V, SOIC package 0.4 1.5 mV
AD8065WARTZ only: TMIN − TMAX 2.6 mV
Input Offset Voltage Drift 1 17 μV/°C
AD8065WARTZ only: TMIN − TMAX 17 μV/°C
Input Bias Current SOIC package 2 6 pA
T
MIN to TMAX 25 125 pA
Input Offset Current 1 10 pA
T
MIN to TMAX 1 125 pA
Open-Loop Gain VO = ±3 V, RL = 1 kΩ 100 113 dB
AD8065WARTZ only: TMIN − TMAX 100 dB
INPUT CHARACTERISTICS
Common-Mode Input Impedance 1000 || 2.1 GΩ || pF
Differential Input Impedance 1000 || 4.5 GΩ || pF
Input Common-Mode Voltage Range
FET Input Range −5 to +1.7 −5.0 to +2.4 V
AD8065WARTZ only: TMIN − TMAX −5 to +1.7 V
Common-Mode Rejection Ratio VCM = −1 V to +1 V −85 −100 dB
V
CM = −1 V to +1 V (SOT-23) −82 −91 dB
AD8065WARTZ only: TMIN − TMAX −82 dB
AD8065/AD8066
Rev. J | Page 5 of 28
Parameter Conditions Min Typ Max Unit
OUTPUT CHARACTERISTICS
Output Voltage Swing RL = 1 kΩ −4.88 to +4.90 −4.94 to +4.95 V
AD8065WARTZ only: TMIN − TMAX −4.88 to +4.90 V
R
L = 150 Ω −4.8 to +4.7 V
Output Current VO = 9 V p-p, SFDR ≥ −60 dBc, f = 500 kHz 35 mA
Short-Circuit Current 90 mA
Capacitive Load Drive 30% overshoot G = +1 20 pF
POWER SUPPLY
Operating Range 5 24 V
AD8065WARTZ only: TMIN − TMAX 5 10 V
Quiescent Current per Amplifier 6.4 7.2 mA
AD8065WARTZ only: TMIN − TMAX 7.2 mA
Power Supply Rejection Ratio ±PSRR −85 −100 dB
AD8065WARTZ only: TMIN − TMAX −85 dB
AD8065/AD8066
Rev. J | Page 6 of 28
SPECIFICATIONS ±12 V
@ TA = 25°C, VS = ±12 V, RL = 1 kΩ, unless otherwise noted.
Table 2.
Parameter Conditions Min Typ Max Unit
DYNAMIC PERFORMANCE
−3 dB Bandwidth G = +1, VO = 0.2 V p-p (AD8065) 100 145 MHz
G = +1, VO = 0.2 V p-p (AD8066) 100 115 MHz
G = +2, VO = 0.2 V p-p 50 MHz
G = +2, VO = 2 V p-p 40 MHz
Bandwidth for 0.1 dB Flatness G = +2, VO = 0.2 V p-p 7 MHz
Input Overdrive Recovery G = +1, −12.5 V to +12.5 V 175 ns
Output Overdrive Recovery G = −1, −12.5 V to +12.5 V 170 ns
Slew Rate G = +2, VO = 4 V step 130 180 V/μs
Settling Time to 0.1% G = +2, VO = 2 V step 55 ns
G = +2, VO = 10 V step 250 ns
NOISE/HARMONIC PERFORMANCE
SFDR fC = 1 MHz, G = +2, VO = 2 V p-p −100 dBc
f
C = 5 MHz, G = +2, VO = 2 V p-p −67 dBc
f
C = 1 MHz, G = +2, VO = 10 V p-p −85 dBc
Third-Order Intercept fC = 10 MHz, RL = 100 Ω 24 dBm
Input Voltage Noise f = 10 kHz 7 nV/√Hz
Input Current Noise f = 10 kHz 1 fA/√Hz
Differential Gain Error NTSC, G = +2, RL = 150 Ω 0.04 %
Differential Phase Error NTSC, G = +2, RL = 150 Ω 0.03 Degrees
DC PERFORMANCE
Input Offset Voltage VCM = 0 V, SOIC package 0.4 1.5 mV
Input Offset Voltage Drift 1 17 μV/°C
Input Bias Current SOIC package 3 7 pA
T
MIN to TMAX 25 pA
Input Offset Current 2 10 pA
T
MIN to TMAX 2 pA
Open-Loop Gain VO = ±10 V, RL = 1 kΩ 103 114 dB
INPUT CHARACTERISTICS
Common-Mode Input Impedance 1000 || 2.1 GΩ || pF
Differential Input Impedance 1000 || 4.5 GΩ || pF
Input Common-Mode Voltage Range
FET Input Range −12 to +8.5 −12.0 to +9.5 V
Common-Mode Rejection Ratio VCM = −1 V to +1 V −85 −100 dB
V
CM = −1 V to +1 V (SOT-23) −82 −91 dB
OUTPUT CHARACTERISTICS
Output Voltage Swing RL = 1 kΩ −11.8 to +11.8 −11.9 to +11.9 V
R
L = 350 Ω −11.25 to +11.5 V
Output Current VO = 22 V p-p, SFDR ≥ −60 dBc, f = 500 kHz 30 mA
Short-Circuit Current 120 mA
Capacitive Load Drive 30% overshoot G = +1 25 pF
POWER SUPPLY
Operating Range 5 24 V
Quiescent Current per Amplifier 6.6 7.4 mA
Power Supply Rejection Ratio ±PSRR −84 −93 dB
AD8065/AD8066
Rev. J | Page 7 of 28
SPECIFICATIONS +5 V
@ TA = 25°C, VS = 5 V, RL = 1 kΩ, unless otherwise noted.
Table 3.
Parameter Conditions Min Typ Max Unit
DYNAMIC PERFORMANCE
−3 dB Bandwidth G = +1, VO = 0.2 V p-p (AD8065) 125 155 MHz
AD8065WARTZ only: TMIN − TMAX 90 MHz
G = +1, VO = 0.2 V p-p (AD8066) 110 130 MHz
G = +2, VO = 0.2 V p-p 50 MHz
G = +2, VO = 2 V p-p 43 MHz
Bandwidth for 0.1 dB Flatness G = +2, VO = 0.2 V p-p 6 MHz
Input Overdrive Recovery Time G = +1, −0.5 V to +5.5 V 175 ns
Output Recovery Time G = −1, −0.5 V to +5.5 V 170 ns
Slew Rate G = +2, VO = 2 V step 105 160 V/μs
AD8065WARTZ only: TMIN − TMAX 123 V/μs
Settling Time to 0.1% G = +2, VO = 2 V step 60 ns
NOISE/HARMONIC PERFORMANCE
SFDR fC = 1 MHz, G = +2, VO = 2 V p-p −65 dBc
f
C = 5 MHz, G = +2, VO = 2 V p-p −50 dBc
Third-Order Intercept fC = 10 MHz, RL = 100 Ω 22 dBm
Input Voltage Noise f = 10 kHz 7 nV/√Hz
Input Current Noise f = 10 kHz 0.6 fA/√Hz
Differential Gain Error NTSC, G = +2, RL = 150 Ω 0.13 %
Differential Phase Error NTSC, G = +2, RL = 150 Ω 0.16 Degrees
DC PERFORMANCE
Input Offset Voltage VCM = 1.0 V, SOIC package 0.4 1.5 mV
AD8065WARTZ only: TMIN − TMAX 2.6 mV
Input Offset Voltage Drift 1 17 μV/ºC
AD8065WARTZ only: TMIN − TMAX 17 μV/ºC
Input Bias Current SOIC package 1 5 pA
T
MIN to TMAX 25 125 pA
Input Offset Current 1 5 pA
T
MIN to TMAX 1 125 pA
Open-Loop Gain VO = 1 V to 4 V (AD8065) 100 113 dB
AD8065WARTZ only: TMIN − TMAX 100 dB
V
O = 1 V to 4 V (AD8066) 90 103 dB
INPUT CHARACTERISTICS
Common-Mode Input Impedance 1000 || 2.1 GΩ || pF
Differential Input Impedance 1000 || 4.5 GΩ || pF
Input Common-Mode Voltage Range
FET Input Range 0 to 1.7 0 to 2.4 V
AD8065WARTZ only: TMIN − TMAX 0 to 1.7 V
Common-Mode Rejection Ratio VCM = 0.5 V to 1.5 V −74 −100 dB
V
CM = 1 V to 2 V (SOT-23) −78 −91 dB
AD8065WARTZ only: TMIN-TMAX −76 dB
OUTPUT CHARACTERISTICS
Output Voltage Swing RL = 1 kΩ 0.1 to 4.85 0.03 to 4.95 V
AD8065WARTZ only: TMIN − TMAX 0.1 to 4.85 V
R
L = 150 Ω 0.07 to 4.83 V
Output Current VO = 4 V p-p, SFDR ≥ −60 dBc, f = 500 kHz 35 mA
Short-Circuit Current 75 mA
Capacitive Load Drive 30% overshoot G = +1 5 pF
AD8065/AD8066
Rev. J | Page 8 of 28
Parameter Conditions Min Typ Max Unit
POWER SUPPLY
Operating Range 5 24 V
AD8065WARTZ only: TMIN − TMAX 5 10 V
Quiescent Current per Amplifier 5.8 6.4 7.0 mA
AD8065WARTZ only: TMIN − TMAX 7.0 mA
Power Supply Rejection Ratio ±PSRR −78 −100 dB
AD8065WARTZ only: TMIN − TMAX −78 dB
AD8065/AD8066
Rev. J | Page 9 of 28
ABSOLUTE MAXIMUM RATINGS
RMS output voltages should be considered. If RL is referenced to
VS−, as in single-supply operation, then the total drive power is
VS × IOUT.
Table 4.
Parameter Rating
Supply Voltage 26.4 V
Power Dissipation See Figure 3
Common-Mode Input Voltage VEE − 0.5 V to VCC + 0.5 V
Differential Input Voltage 1.8 V
Storage Temperature Range −65°C to +125°C
Operating Temperature Range −40°C to +85°C
AD8065WARTZ Only −40°C to +105°C
Lead Temperature
(Soldering, 10 sec)
300°C
If the rms signal levels are indeterminate, then consider the
worst case, when VOUT = VS/4 for RL to midsupply.
()
()
L
S
SS
DR
V
IVP
2
4/
+×=
In single-supply operation with RL referenced to VS−, worst case
is VOUT = VS/2.
MAXIMUM POWER DISSIPATION (W)
0
0.5
1.0
1.5
2.0
200–40 –20–60 40 60 80 100
AMBIENT TEMPERATURE (°C)
02916-E-003
MSOP-8
SOIC-8
SOT-23-5
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
MAXIMUM POWER DISSIPATION
The maximum safe power dissipation in the AD8065/AD8066
packages is limited by the associated rise in junction temperature
(TJ) on the die. The plastic encapsulating the die locally reaches
the junction temperature. At approximately 150°C, which is the
glass transition temperature, the plastic changes its properties.
Even temporarily exceeding this temperature limit can change
the stresses that the package exerts on the die, permanently
shifting the parametric performance of the AD8065/AD8066.
Exceeding a junction temperature of 175°C for an extended
time can result in changes in the silicon devices, potentially
causing failure.
Figure 3. Maximum Power Dissipation vs. Temperature for a 4-Layer Board
Airflow increases heat dissipation, effectively reducing θJA. Also,
more metal directly in contact with the package leads from
metal traces, through holes, ground, and power planes reduce
the θJA. Care must be taken to minimize parasitic capacitances
at the input leads of high speed op amps as discussed in the
Layout, Grounding, and Bypassing Considerations section.
The still air thermal properties of the package and PCB (θJA),
ambient temperature (TA), and total power dissipated in the
package (PD) determine the junction temperature of the die.
The junction temperature can be calculated by
Figure 3 shows the maximum safe power dissipation in the
package vs. the ambient temperature for the SOIC (125°C/W),
SOT-23 (180°C/W), and MSOP (150°C/W) packages on a
JEDEC standard 4-layer board. θJA values are approximations.
TJ = TA + (PD × θJA) OUTPUT SHORT CIRCUIT
The power dissipated in the package (PD) is the sum of the
quiescent power dissipation and the power dissipated in the
package due to the load drive for all outputs. The quiescent
power is the voltage between the supply pins (VS) times the
quiescent current (IS). Assuming the load (RL) is referenced to
midsupply, then the total drive power is VS /2 × IOUT, some of
which is dissipated in the package and some in the load (VOUT ×
IOUT). The difference between the total drive power and the load
power is the drive power dissipated in the package.
Shorting the output to ground or drawing excessive current for
the AD8065/AD8066 will likely cause catastrophic failure.
ESD CAUTION
(
)
PowerLoadPowerDriveTotalPowerQuiescentPD−+=
()
L
OUT
L
OUT
S
SS
DR
V
R
VV
IVP
2
2−
⎟
⎠
⎞
⎜
⎝
⎛×+×=
AD8065/AD8066
Rev. J | Page 10 of 28
TYPICAL PERFORMANCE CHARACTERISTICS
Default Conditions: ±5 V, CL = 5 pF, RL = 1 kΩ, VOUT = 2 V p-p, Temperature = 25°C.
–6
–3
0
3
6
9
12
15
18
21
24
GAIN (dB)
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-004
G = +10 V
O
= 200mV p-p
G = +5
G = +2
G = +1
Figure 4. Small Signal Frequency Response for Various Gains
–6
–4
–2
0
2
4
6
GAIN (dB)
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-005
V
O
= 200mV p-p
G = +1
V
S
= +5V
V
S
= ±12V
V
S
= ±5V
Figure 5. Small Signal Frequency Response for Various Supplies
(See Figure 42)
–5
–4
–3
–2
–1
0
1
2
GAIN (dB)
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-006
V
O
= 2V p-p
G = +1
V
S
= ±12V
V
S
= ±5V
Figure 6. Large Signal Frequency Response for Various Supplies
(See Figure 42)
5.9
6.0
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
GAIN (dB)
FREQUENCY (MHz)
0.1 101 100
02916-E-007
R
L
= 150
Ω
G = +2 V
OUT
= 0.2V p-p
V
OUT
= 0.7V p-p
V
OUT
= 1.4V p-p
Figure 7. 0.1 dB Flatness Frequency Response (See Figure 43)
3
4
5
6
7
8
9
GAIN (dB)
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-008
V
O
= 200mV p-p
G = +2
V
S
= ±12V
V
S
= ±5V
V
S
= +5V
Figure 8. Small Signal Frequency Response for Various Supplies
(See Figure 43)
0
1
2
3
4
5
GAIN (dB)
6
7
8
FREQUENC Y ( M Hz )
10.1 10 100 1000
02916-009
G = +2
V
S
= ±12V
V
S
= ±5V
V
S
= +5V
V
O
= 2V p-p
Figure 9. Large Signal Frequency Response for Various Supplies
(See Figure 43)
AD8065/AD8066
Rev. J | Page 11 of 28
–9
–6
–3
0
3
6
9
GAIN (dB)
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-010
G = +1 C
L
= 25pF
C
L
= 25pF
R
SNUB
= 20Ω
C
L
= 20pF
C
L
= 5pF
V
O
= 200mV p-p
Figure 10. Small Signal Frequency Response for Various CLOAD (See Figure 42)
–8
–6
–4
–2
0
2
GAIN (dB)
4
6
8
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-011
G = +2
V
OUT
= 0.2V p-p
V
OUT
= 2V p-p
V
OUT
= 4V p-p
Figure 11. Frequency Response for Various Output Amplitudes
(See Figure 43)
–4
–2
0
2
4
6
8
10
12
14
GAIN (dB)
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-012
G = +2
R
F
= R
G
= 1kΩ,
R
S
= 500Ω
R
F
= R
G
= 500Ω,
R
S
= 250Ω
R
F
= R
G
= 500Ω,
R
S
= 250Ω,
C
F
= 2.2pF
R
F
= R
G
= 1kΩ,
R
S
= 500Ω,
C
F
= 3.3pF
V
O
= 200mV p-p
Figure 12. Small Signal Frequency Response for Various RF/CF (See Figure 43)
–8
–6
–4
–2
0
2
GAIN (dB)
4
6
8
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-013
C
L
= 25pF
C
L
= 55pF
C
L
= 5pF
V
O
= 200mV p-p
G = +2
Figure 13. Small Signal Frequency Response for Various CLOAD (See Figure 43)
0
1
2
3
4
5
GAIN (dB)
6
7
8
FREQUENCY (MHz)
10.1 10 100 1000
02916-E-014
R
L
= 100Ω
R
L
= 1kΩ
V
O
= 200mV p-p
G = +2
Figure 14. Small Signal Frequency Response for Various RLOAD (See Figure 43)
–180
–120
–60
0
60
120
PHASE (DEGREES)
–20
0
20
40
60
80
OPEN-LOOP GAIN (dB)
0.01 0.1 1 10 100 1000
FREQUENCY (MHz)
02916-E-015
PHASE
GAIN
Figure 15. Open-Loop Response
AD8065/AD8066
Rev. J | Page 12 of 28
–120
–110
–100
–90
–80
–70
–60
–50
–40
–30
DISTORTION (dBc)
FREQUENCY (MHz)
0.1 101 100
02916-E-016
HD3 R
L
= 150Ω
HD2 R
L
= 150Ω
HD3 R
L
= 1kΩ
HD2 R
L
= 1kΩ
G = +2
Figure 16. Harmonic Distortion vs. Frequency for Various Loads
(See Figure 43)
–120
–110
–100
–90
–80
–70
–60
–50
–40
–30
DISTORTION (dBc)
01234 6 105 789 1211 1413 15
OUTPUT AMPLITUDE (V p-p)
02916-E-017
HD3 R
L
= 150Ω
HD2 R
L
= 150Ω
HD3 R
L
= 300Ω
HD2 R
L
= 300Ω
G = +2
V
S
= ±12V
F = 1MHz
Figure 17. Harmonic Distortion vs. Amplitude for Various Loads VS = ±12 V
(See Figure 43)
15
20
25
30
35
40
45
50
INTERCEPT POINT (dBm)
FREQUENCY (MHz)
110
02916-E-018
V
S
= ±12V R
L
= 100Ω
V
S
= ±5V
V
S
= +5V
Figure 18. Third-Order Intercept vs. Frequency and Supply Voltage
–110
–100
–90
–80
–70
–60
–50
–40
DISTORTION (dBc)
FREQUENCY (MHz)
0.1 101 100
02916-E-019
HD2 G = +2
HD3 G = +2
HD2 G = +1
HD3 G = +1
Figure 19. Harmonic Distortion vs. Frequency for Various Gains
(See Figure 42 and Figure 43)
–120
–110
–100
–90
–80
–70
–60
–50
–40
–30
–20
DISTORTION (dBc)
FREQUENCY (MHz)
0.1 1.0 10.0
02916-E-020
HD2 V
O
= 20V p-p
HD3 V
O
= 20V p-p
HD2 V
O
= 10V p-p
HD3 V
O
= 10V p-p
HD2 V
O
= 2V p-p
HD3 V
O
= 2V p-p
V
S
= ±12V
G = +2
Figure 20. Harmonic Distortion vs. Frequency for Various Amplitudes
(See Figure 43)
NOISE (nV/ Hz)
1
10
100
100k10k100 1k10 1M 10M 100M 1G
FREQUENCY (Hz)
02916-E-021
Figure 21. Voltage Noise
AD8065/AD8066
Rev. J | Page 13 of 28
02916-022
G = +1
50mV/DIV 25ns/DIV
Figure 22. Small Signal Transient Response 5 V Supply (See Figure 42)
02916-023
G = +1
2V/DIV 50ns/DIV
V
S
= ±12V
V
OUT
= 2V p-p
V
OUT
= 4V p-p
V
OUT
= 10V p-p
Figure 23. Large Signal Transient Response (See Figure 42)
02916-024
2.0V/DIV 100ns/DIV
G = –1
V
S
= ±5V
Figure 24. Output Overdrive Recovery (See Figure 44)
02916-025
G = +1
50mV/DIV 25ns/DIV
C
L
= 5pF
C
L
= 20pF
Figure 25. Small Signal Transient Response ±5 V (See Figure 42)
02916-026
5µs
G = +2
2V/DIV 50ns/DIV
V
S
= ±12V
V
OUT
= 10V p-p
V
OUT
= 2V p-p
Figure 26. Large Signal Transient Response (See Figure 43)
02916-027
2.0V/DIV 100ns/DIV
G = +1
V
S
= ±5V
Figure 27. Input Overdrive Recovery (See Figure 42)
AD8065/AD8066
Rev. J | Page 14 of 28
02916-E-028
t = 0
64
μ
s/DIV
2mV/DIV
+0.1%
–0.1%
V
IN
= 140mV/DIV
V
OUT
– 2V
IN
Figure 28. Long-Term Settling Time (See Figure 49)
–30
–25
–20
–15
–10
–5
0
INPUT BIAS CURRENT (pA)
45 5525 35 65 75 85
TEMPERATURE (°C)
02916-E-029
–I
b
+I
b
Figure 29. Input Bias Current vs. Temperature
–0.3
–0.2
–0.1
0
0.1
0.2
0.3
OFFSET VOLTAGE (mV)
–14 –10–12 –8–6–4 0 8–2 2 4 6 10 12 14
COMMON-MODE VOLTAGE (V)
02916-E-030
V
S
= ±12V
V
S
= ±5V
V
S
= +5V
Figure 30. Input Offset Voltage vs. Common-Mode Voltage
02916-E-031
+0.1%
2mV/DIV 10ns/DIV
–0.1% t = 0
V
OUT
– 2V
IN
V
IN
= 500mV/DIV
Figure 31. 0.1% Short-Term Settling Time (See Figure 49)
02916-E-032
0
I
b
(μA)
36
30
24
18
12
6
–5
–15
–25
–30
0
I
b
(pA)
–12 8–2–10 0
–8 2–6 4–4 6
COMMON-MODEVOLTAGE (V)
10 12
42
–Ib
+Ib
–Ib
+Ib
FET INPUT STAGE BJT INPUT STAGE
–20
–10
5
10
Figure 32. Input Bias Current vs. Common-Mode Voltage Range
(See the Input and Output Overload Behavior Section)
02916-E-033
INPUT OFFSET VOLTAGE (mV)
35
15
0
–2.0 2.0–1.5 –1.0 –0.5 0 0.5 1.0 1.5
30
20
10
5
40
25
N = 299
SD = 0.388
MEAN = –0.069
Figure 33. Input Offset Voltage
AD8065/AD8066
Rev. J | Page 15 of 28
–100
–90
–80
–70
–60
–50
–40
–30
CMRR (dB)
FREQUENCY (MHz)
0.1 101 100
02916-E-034
V
S
= ±12V
V
S
= ±5V
Figure 34. CMRR vs. Frequency (See Figure 46)
0
0.05
0.10
0.15
0.20
0.25
0.30
OUTPUT SATURATION VOLTAGE (V)
I
LOAD
(mA)
1002030
02916-E-035
V
CC
– V
OH
V
OL
– V
EE
40
Figure 35. Output Saturation Voltage vs. Output Load Current
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
PSRR (dB)
0.01 0.1 1 10 100 1000
FREQUENCY (MHz)
02916-E-036
–PSRR
+PSRR
Figure 36. PSRR vs. Frequency (See Figure 48 and Figure 50)
0
0.01
0.1
1
10
100
OUTPUT IMPEDANCE (Ω)
10k 100k100 1k 1M 10M 100M
FREQUENCY (Hz)
02916-E-037
G = +2
G = +1
Figure 37. Output Impedance vs. Frequency (See Figure 45 and Figure 47)
30
40
50
60
70
80
OUTPUT SATURATION VOLTAGE (mV)
45 5525 35 65 75 85
TEMPERATURE (°C)
02916-E-038
V
CC
– V
OH
V
OL
– V
EE
Figure 38. Output Saturation Voltage vs. Temperature
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
CROSSTALK (dB)
FREQUENCY (MHz)
0.1 101 100
02916-E-039
V
IN
= 2V p-p
G = +1
B TO A
A TO B
Figure 39. Crosstalk vs. Frequency (See Figure 51)
AD8065/AD8066
Rev. J | Page 16 of 28
6.25
6.30
6.35
6.40
6.45
6.50
6.55
6.60
SUPPLY CURRENT (mA)
020–40 –20 40 60 80
TEMPERATURE (°C)
02916-E-040
V
S
= ±12V
V
S
= +5V
V
S
= ±5V
Figure 40. Quiescent Supply Current vs. Temperature for Various
Supply Voltages
80
85
90
95
100
105
110
115
120
125
OPEN-LOOP GAIN (dB)
I
LOAD
(mA)
1002030
02916-E-041
40
V
S
= ±12V
V
S
= +5V
V
S
= ±5V
Figure 41. Open-Loop Gain vs. Load Current for Various Supply Voltages
AD8065/AD8066
Rev. J | Page 17 of 28
TEST CIRCUITS
SOIC-8 Pinout
AD8065
+V
CC
V
IN
–V
EE
4.7μF
0.1μF
24.9Ω
R
SNUB
0.1μF
4.7μF
C
LOAD
FET PROBE
49.9Ω1kΩ
02916-E-042
Figure 42. G = +1
02916-E-043
AD8065
+V
CC
V
IN
–V
EE
4.7μF
0.1μF
2.2pF
R
SNUB
0.1μF
4.7μF
49.9Ω
499Ω499Ω
249ΩC
LOAD
FET PROBE
1kΩ
Figure 43. G = +2
V
IN
49.9Ω
AD8065
+V
CC
–V
EE
4.7μF
0.1μF
2.2pF
0.1μF
4.7μF
499Ω499Ω
249Ω
FET PROBE
1kΩ
02916-E-044
Figure 44. G = −1
AD8065
+V
CC
–V
EE
4.7μF
0.1μF
24.9Ω
0.1μF
4.7μF
NETWORK ANALYZER S22
02916-E-045
Figure 45. Output Impedance G = +1
AD8065/AD8066
Rev. J | Page 18 of 28
V
IN
49.9Ω
AD8065
+V
CC
–V
EE
4.7μF
0.1μF
0.1μF
4.7μF
499Ω499Ω
FET PROBE
1kΩ
499Ω499Ω
02916-E-046
Figure 46. CMRR
AD8065
+V
CC
–V
EE
0.1μF
4.7μF
499Ω499Ω
249ΩNETWORK ANALYZER
S22
4.7μF
0.1μF
02916-E-047
Figure 47. Output Impedance G = +2
AD8065
–V
EE
24.9Ω
0.1μF
4.7μF
+V
CC
FET PROBE
1kΩ
V
IN
1V p-p
49.9Ω
02916-E-048
Figure 48. Positive PSRR
AD8065
+V
CC
V
IN
–V
EE
4.7μF
0.1μF
2.2pF
976Ω
0.1μF
4.7μF
499Ω499Ω
249Ω
TO SCOPE
49.9Ω
49.9Ω
02916-E-049
Figure 49. Settling Time
AD8065/AD8066
Rev. J | Page 19 of 28
AD8065
+V
CC
–V
EE
4.7μF
0.1μF
FET PROBE
49.9Ω
24.9Ω
V
IN
1V p-p
1kΩ
02916-E-050
Figure 50. Negative PSRR
24.9Ω
49.9Ω
24.9Ω
1kΩ
0.1μF
4.7μF
V
IN
+5V
–5V
1kΩ
DRIVE SIDE
RECEIVE SIDE
AD8066
AD8066
0.1μF
4.7μF
FET PROBE
02916-E-051
Figure 51. Crosstalk—AD8066
249Ω
0.1μF
V
IN
1.5V
1.5V
1.5V
4.7μF
499Ω
499Ω
5V
49.9Ω
2.2pF
1kΩ
FET PROBE
AD8065
02916-E-052
Figure 52. Single Supply
AD8065/AD8066
Rev. J | Page 20 of 28
THEORY OF OPERATION
The AD8065/AD8066 are voltage feedback operational amplifiers
that combine a laser-trimmed JFET input stage with the Analog
Devices eXtra Fast Complementary Bipolar (XFCB) process,
resulting in an outstanding combination of precision and speed.
The supply voltage range is from 5 V to 24 V. The amplifiers feature
a patented rail-to-rail output stage capable of driving within 0.5 V
of either power supply while sourcing or sinking up to 30 mA.
Also featured is a single-supply input stage that handles common-
mode signals from below the negative supply to within 3 V of the
positive rail. Operation beyond the JFET input range is possible
because of an auxiliary bipolar input stage that functions with
input voltages up to the positive supply. The amplifiers operate as
if they have a rail-to-rail input and exhibit no phase reversal
behavior for common-mode voltages within the power supply.
With voltage noise of 7 nV/√Hz and −88 dBc distortion for
1 MHz, 2 V p-p signals, the AD8065/AD8066 are a great choice
for high resolution data acquisition systems. Their low noise,
sub-pA input current, precision offset, and high speed make
them superb preamps for fast photodiode applications. The
speed and output drive capability of the AD8065/AD8066 also
make them useful in video applications.
CLOSED-LOOP FREQUENCY RESPONSE
The AD8065/AD8066 are classic voltage feedback amplifiers
with an open-loop frequency response that can be approximated as
the integrator response shown in Figure 53. Basic closed-loop
frequency response for inverting and noninverting configurations
can be derived from the schematics shown.
NONINVERTING CLOSED-LOOP FREQUENCY
RESPONSE
Solving for the transfer function
()
()
G
crossover
G
F
F
G
crossover
I
O
RfsRR
RRf
V
V
××π++
+×π
=2
2
where fcrossover is the frequency where the amplifier’s open-loop
gain equals 0 db
At dc
G
G
F
I
O
R
RR
V
V+
=
Closed-loop −3 dB frequency
G
F
G
crossover
3dB RR
R
ff +
×=
−
INVERTING CLOSED-LOOP FREQUENCY
RESPONSE
()
G
crossover
G
F
F
crossover
I
O
RfRRs
Rf
V
V
××π++
××π−
=2
2
At dc
G
F
I
O
R
R
V
V−=
Closed-loop −3 dB frequency
GF
G
crossoverdB RR
R
ff +
×=
−3
R
F
A
V
O
R
G
V
I
V
E
FREQUENCY (MHz)
80
60
0.01 100
OPEN-LOOP GAIN (A) (dB)
0.1 101
40
20
0
f
crossover
= 65MHz
A = (2π×f
crossover
)/s
R
F
V
E
A
V
O
R
G
V
I
02916-E-053
Figure 53. Open-Loop Gain vs. Frequency and Basic Connections
AD8065/AD8066
Rev. J | Page 21 of 28
The closed-loop bandwidth is inversely proportional to the noise
gain of the op amp circuit, (RF + RG )/RG. This simple model is
accurate for noise gains above 2. The actual bandwidth of circuits
with noise gains at or below 2 is higher than those predicted
with this model due to the influence of other poles in the
frequency response of the real op amp.
V
O
R
F
A
R
G
V
I
I
b
–
R
S
I
b
+
+V
OS
–
02916-E-054
Figure 54. Voltage Feedback Amplifier DC Errors
Figure 54 shows a voltage feedback amplifier’s dc errors. For
both inverting and noninverting configurations
()
⎟
⎠
⎞
⎜
⎝
⎛+
+×−
⎟
⎠
⎞
⎜
⎝
⎛+
×= −+
G
F
G
OS
F
b
G
F
G
S
b
OR
RR
VRI
R
RR
RIerrorV
The voltage error due to Ib+ and Ib– is minimized if RS = RF || RG
(though with the AD8065 input currents at typically less than
20 pA over temperature, this is likely not a concern). To include
common-mode and power supply rejection effects, total VOS can be
modeled
CMR
V
PSR
V
VV CMS
nom
OSOS
ΔΔ ++=
nom
OS
V is the offset voltage specified at nominal conditions,
ΔVS is the change in power supply from nominal conditions,
PSR is the power supply rejection, ΔVCM is the change in common-
mode voltage from nominal conditions, and CMR is the common-
mode rejection.
WIDEBAND OPERATION
Figure 42 through Figure 44 show the circuits used for wideband
characterization for gains of +1, +2, and −1. Source impedance at
the summing junction (RF || RG) forms a pole in the amplifier’s loop
response with the amplifier’s input capacitance of 6.6 pF. This
can cause peaking and ringing if the time constant formed is too
low. Feedback resistances of 300 Ω to 1 kΩ are recommended,
because they do not unduly load down the amplifier, and the
time constant formed will not be too low. Peaking in the
frequency response can be compensated for with a small
capacitor (CF) in parallel with the feedback resistor, as
illustrated in Figure 12. This shows the effect of different
feedback capacitances on the peaking and bandwidth for a
noninverting G = +2 amplifier.
For the best settling times and the best distortion, the impedances
at the AD8065/AD8066 input terminals should be matched. This
minimizes nonlinear common-mode capacitive effects that can
degrade ac performance.
Actual distortion performance depends on a number of
variables:
• The closed-loop gain of the application
• Whether it is inverting or noninverting
• Amplifier loading
• Signal frequency and amplitude
• Board layout
Also see Figure 16 to Figure 20. The lowest distortion is obtained
with the AD8065 used in low gain inverting applications,
because this eliminates common-mode effects. Higher closed-
loop gains result in worse distortion performance.
INPUT PROTECTION
The inputs of the AD8065/AD8066 are protected with back-to-
back diodes between the input terminals as well as ESD diodes
to either power supply. This results in an input stage with picoamps
of input current that can withstand up to 1500 V ESD events
(human body model) with no degradation.
Excessive power dissipation through the protection devices
destroys or degrades the performance of the amplifier. Differ-
ential voltages greater than 0.7 V result in an input current of
approximately (|V+ − V−| 0.7 V)/RI, where RI is the resistance in
series with the inputs.
For input voltages beyond the positive supply, the input current
is approximately (VI − VCC − 0.7)/RI. Beyond the negative supply,
the input current is about (VI − VEE + 0.7)/RI. If the inputs of the
amplifier are to be subjected to sustained differential voltages
greater than 0.7 V, or to input voltages beyond the amplifier
power supply, input current should be limited to 30 mA by an
appropriately sized input resistor (RI), as shown in Figure 55.
R
I
V
I
V
O
AD8065
R
I
>(| V+–V
–
| – 0.7V)
30mA
FOR LARGE | V
+
–V
–
|
R
I
>(V
I
–V
EE
– 0.7V)
30mA
R
I
>(V
I
–V
EE
+ 0.7V)
30mA
FOR V
I
BEYOND
SUPPLY VOLTAGES
02916-E-055
Figure 55. Current-Limiting Resistor
AD8065/AD8066
Rev. J | Page 22 of 28
THERMAL CONSIDERATIONS INPUT AND OUTPUT OVERLOAD BEHAVIOR
With 24 V power supplies and 6.5 mA quiescent current, the
AD8065 dissipates 156 mW with no load. The AD8066 dissipates
312 mW. This can lead to noticeable thermal effects, especially
in the small SOT-23-5 (thermal resistance of 160°C/W). VOS
temperature drift is trimmed to guarantee a maximum drift of
17 μV/°C, so it can change up to 0.425 mV due to warm-up
effects for an AD8065/AD8066 in a SOT-23-5 package on 24 V.
A simplified schematic of the AD8065/AD8066 input stage is
shown in Figure 56. This shows the cascoded N-channel JFET
input pair, the ESD and other protection diodes, and the
auxiliary NPN input stage that eliminates any phase inversion
behavior. When the common-mode input voltage to the amplifier
is driven to within approximately 3 V of the positive power supply,
the input JFET’s bias current turns off and the bias of the NPN
pair turns on, taking over control of the amplifier. The NPN
differential pair now sets the amplifier’s offset, and the input
bias current is now in the range of several tens of microamps.
This behavior is shown in Figure 32. Normal operation resumes
when the common-mode voltage goes below the 3 V from the
positive supply threshold.
Ib increases by a factor of 1.7 for every 10°C rise in temperature.
Ib is close to five times higher at 24 V supplies as opposed to a
single 5 V supply.
Heavy loads increase power dissipation and raise the chip
junction temperature as described in the Maximum Power
Dissipation section. Care should be taken not to exceed the
rated power dissipation of the package. The output transistors of the rail-to-rail output stage have
circuitry to limit the extent of their saturation when the output
is overdriven. This helps output recovery time. Output recovery
from a 0.5 V output overdrive on a ±5 V supply is shown in
Figure 24.
V
THRESHOLD
VBIAS
S
V
P
TO REST OF AMP
V
CC
S
V
N
R1
Q2 Q5
Q3
Q1 Q6
Q7
Q4
R5
D1 R6
R3
R4
R2 R8
R7
D2
D3 D4
–V
EE
I
T1
I
T2
02916-E-056
Figure 56. Simplified Input Stage
AD8065/AD8066
Rev. J | Page 23 of 28
LAYOUT, GROUNDING, AND BYPASSING CONSIDERATIONS
POWER SUPPLY BYPASSING
Power supply pins are actually inputs and care must be taken so
that a noise-free stable dc voltage is applied. The purpose of bypass
capacitors is to create low impedances from the supply to ground at
all frequencies, thereby shunting or filtering most of the noise.
Decoupling schemes are designed to minimize the bypassing
impedance at all frequencies with a parallel combination of
capacitors. 0.1 μF (X7R or NPO) chip capacitors are critical
and should be as close as possible to the amplifier package.
The 4.7 μF tantalum capacitor is less critical for high frequency
bypassing, and, in most cases, only one is needed per board at
the supply inputs.
GROUNDING
A ground plane layer is important in densely packed PC boards
to spread the current minimizing parasitic inductances. However,
an understanding of where the current flows in a circuit is critical
to implementing effective high speed circuit design. The length
of the current path is directly proportional to the magnitude of
parasitic inductances and, therefore, the high frequency impedance
of the path. High speed currents in an inductive ground return
create unwanted voltage noise.
The length of the high frequency bypass capacitor leads is most
critical. A parasitic inductance in the bypass grounding works
against the low impedance created by the bypass capacitor. Place
the ground leads of the bypass capacitors at the same physical
location. Because load currents flow from the supplies as well,
the ground for the load impedance should be at the same physical
location as the bypass capacitor grounds. For the larger value
capacitors, which are effective at lower frequencies, the current
return path distance is less critical.
LEAKAGE CURRENTS
Poor PC board layout, contaminants, and the board insulator
material can create leakage currents that are much larger than
the input bias current of the AD8065/AD8066. Any voltage
differential between the inputs and nearby runs sets up leakage
currents through the PC board insulator, for example, 1 V/100 GΩ
= 10 pA. Similarly, any contaminants on the board can create
significant leakage (skin oils are a common problem). To reduce
leakage significantly, put a guard ring (shield) around the inputs
and input leads that are driven to the same voltage potential as
the inputs. This way there is no voltage potential between the
inputs and surrounding area to set up any leakage currents.
For the guard ring to be completely effective, it must be driven
by a relatively low impedance source and should completely
surround the input leads on all sides, above and below, using
a multilayer board.
Another effect that can cause leakage currents is the charge
absorption of the insulator material itself. Minimizing the
amount of material between the input leads and the guard ring
helps to reduce the absorption. Also, low absorption materials,
such as Teflon® or ceramic, could be necessary in some instances.
INPUT CAPACITANCE
Along with bypassing and ground, high speed amplifiers can be
sensitive to parasitic capacitance between the inputs and ground.
A few pF of capacitance reduces the input impedance at high
frequencies, in turn increasing the amplifier’s gain, causing peaking
of the frequency response or even oscillations, if severe enough.
It is recommended that the external passive components connected
to the input pins be placed as close as possible to the inputs to
avoid parasitic capacitance. The ground and power planes must
be kept at a small distance from the input pins on all layers of
the board.
OUTPUT CAPACITANCE
To a lesser extent, parasitic capacitances on the output can cause
peaking and ringing of the frequency response. There are two
methods to effectively minimize their effect:
• As shown in Figure 57, put a small value resistor (RS) in
series with the output to isolate the load capacitor from the
amp’s output stage. A good value to choose is 20 Ω (see
Figure 10).
• Increase the phase margin with higher noise gains or add
a pole with a parallel resistor and capacitor from −IN to
the output.
R
S
= 20Ω
V
I
AD8065
C
L
V
O
02916-E-057
Figure 57. Output Isolation Resistor
AD8065/AD8066
Rev. J | Page 24 of 28
R
SH
= 10
11
Ω
V
O
R
F
C
F
C
M
R
F
C
M
C
D
C
F
+C
S
C
S
V
B
I
PHOTO
02916-E-058
Figure 58. Wideband Photodiode Preamp
INPUT-TO-OUTPUT COUPLING
To minimize capacitive coupling between the inputs and output,
the output signal traces should not be parallel with the inputs.
WIDEBAND PHOTODIODE PREAMP
Figure 58 shows an I/V converter with an electrical model of a
photodiode. The basic transfer function is
FF
F
PHOTO
OUT RsC
RI
V+
×
=1
where IPHOTO is the output current of the photodiode, and the
parallel combination of RF and CF sets the signal bandwidth.
The stable bandwidth attainable with this preamp is a function
of RF, the gain bandwidth product of the amplifier, and the total
capacitance at the amplifier’s summing junction, including CS
and the amplifier input capacitance. RF and the total capacitance
produce a pole in the amplifier’s loop transmission that can
result in peaking and instability. Adding CF creates a 0 in the
loop transmission that compensates for the pole’s effect and
reduces the signal bandwidth. It can be shown that the signal
bandwidth resulting in a 45° phase margin (f(45)) is defined by
()
S
F
CR
CR
f
f××π
=2
45
where fCR is the amplifier crossover frequency, RF is the feedback
resistor, and CS is the total capacitance at the amplifier summing
junction (amplifier + photodiode + board parasitics).
The value of CF that produces f(45) can be shown to be
CR
F
S
FfR
C
C××π
=2
The frequency response in this case shows about 2 dB of
peaking and 15% overshoot. Doubling CF and cutting the
bandwidth in half results in a flat frequency response with
about 5% transient overshoot.
The preamp’s output noise over frequency is shown in Figure 59.
FREQUENCY (Hz)
VOLTAGE NOISE (nV/ Hz)
2πRFCF
2πRF(CF+C
S+C
M+2C
D)
(CS+C
M+2C
D+C
F)/CF
RF NOISE
VEN (CF+C
S+C
M+ 2CD)/CF
f
3
f
2
f
3=
VEN
f
1
f
2=
f
1=1
1
f
CR
NOISE DUE TO AMPLIFIER
02916-E-059
Figure 59. Photodiode Voltage Noise Contributions
The pole in the loop transmission translates to a 0 in the
amplifier’s noise gain, leading to an amplification of the input
voltage noise over frequency. The loop transmission 0
introduced by CF limits the amplification. The noise gain
bandwidth extends past the preamp signal bandwidth and is
eventually rolled off by the decreasing loop gain of the
amplifier. Keeping the input terminal impedances matched is
recommended to eliminate common-mode noise peaking
effects, which adds to the output noise.
Integrating the square of the output voltage noise spectral
density over frequency and then taking the square root allows
users to obtain the total rms output noise of the preamp. Table 5
summarizes approximations for the amplifier and feedback and
source resistances. Noise components for an example preamp
with RF = 50 kΩ, CS = 15 pF, and CF = 2 pF (bandwidth of about
1.6 MHz) are also listed.
AD8065/AD8066
Rev. J | Page 25 of 28
Table 5. RMS Noise Contributions of Photodiode Preamp
Contributor Expression RMS Noise with RF = 50 kΩ, CS = 15 pF, CF = 2 pF
RF (×2) 57142 .fRkT 2
F×××× 64.5 μV
Amp to f1 1
fVEN × 2.4 μV
Amp (f2 – f1)
12
F
DFM
Sff
C
CCCC
VEN −×
+++
×2
31 μV
Amp to (past f2) 57.1
2××
+++
×3
F
FDM
Sf
C
CCCC
VEN
260 μV
270 μV (Total)
V
CC
V
EE
1/2
AD8066
4.7μF
0.1μF
R
S1
4.7μF
0.1μF
V
N
2.2pF
500Ω
R2
V
P
1/2
AD8066
4.7μF
0.1μF
4.7μF
0.1μF
AD8065
4.7μF
0.1μF
4.7μF
0.1μF
V
O
R
G
V
CC
V
EE
V
CC
V
EE
500Ω
R4
R
S2
500Ω
R1
500Ω
R3
R
F
= 500Ω
2.2pF
R
F
= 500Ω
02916-E-060
Figure 60. High Speed Instrumentation Amplifier
HIGH SPEED JFET INPUT INSTRUMENTATION
AMPLIFIER
Figure 60 shows an example of a high speed instrumentation
amplifier with high input impedance using the
AD8065/AD8066. The dc transfer function is
()
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛+−=
G
PN
OUT R
VVV 1000
1
For G = +1, it is recommended that the feedback resistors for
the two preamps be set to a low value (for instance 50 Ω for
50 Ω source impedance). The bandwidth for G = +1 is 50 MHz.
For higher gains, the bandwidth is set by the preamp, equaling
(
)
(
)
F
GCR
3dB RRfInamp ××=
−2/
Common-mode rejection of the in-amp is primarily
determined by the match of the resistor ratios R1:R2 to R3:R4.
It can be estimated
()
()
211
21
δδ+
δ−δ
=
CM
O
V
V
The summing junction impedance for the preamps is equal to
RF || 0.5(RG). This is the value to be used for matching purposes.
AD8065/AD8066
Rev. J | Page 26 of 28
VIDEO BUFFER
The output current capability and speed of the AD8065 make it
useful as a video buffer, shown in Figure 61.
The G = +2 configuration compensates for the voltage division
of the signal due to the signal termination. This buffer maintains
0.1 dB flatness for signals up to 7 MHz, from low amplitudes up
to 2 V p-p (see Figure 7). Differential gain and phase have been
measured to be 0.02% and 0.028°, respectively, at ±5 V supplies.
+V
S
–V
S
4.7μF
0.1μF
2.2pF
499Ω
249Ω
75Ω
499Ω
V
I
AD8065
4.7μF
0.1μF75ΩV
O
+
–+
–
02916-E-061
Figure 61. Video Buffer
AD8065/AD8066
Rev. J | Page 27 of 28
OUTLINE DIMENSIONS
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
COMPLIANT TO JEDEC STANDARDS MS-012-AA
012407-A
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
0.50 (0.0196)
0.25 (0.0099) 45°
8°
0°
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0040)
4
1
85
5.00(0.1968)
4.80(0.1890)
4.00 (0.1574)
3.80 (0.1497)
1.27 (0.0500)
BSC
6.20 (0.2441)
5.80 (0.2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
Figure 62. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body (R-8)
Dimensions shown in millimeters and (inches)
COMP LI ANT TO JEDE C STANDARDS MO-178- AA
121608-A
10°
5°
0°
SEATING
PLANE
1.90
BSC
0.95 BSC
0.20
BSC
5
123
4
3.00
2.90
2.80
3.00
2.80
2.60
1.70
1.60
1.50
1.30
1.15
0.90
0
.15 MAX
0
.05 MIN
1.45 MAX
0.95 MIN
0.20 MAX
0.08 MIN
0.50 MAX
0.35 MIN
0.55
0.45
0.35
Figure 63. 5-Lead Small Outline Transistor Package [SOT-23]
(RJ-5)
Dimensions shown in millimeters
COMPLIANT TO JEDEC STANDARDS MO-187-AA
100709-B
6°
0°
0.80
0.55
0.40
4
8
1
5
0.65 BSC
0.40
0.25
1.10 MAX
3.20
3.00
2.80
COPLANARITY
0.10
0.23
0.09
3.20
3.00
2.80
5.15
4.90
4.65
PIN 1
IDENTIFIER
15° MAX
0.95
0.85
0.75
0.15
0.05
Figure 64. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
AD8065/AD8066
Rev. J | Page 28 of 28
ORDERING GUIDE
Model1, 2 Temperature Range Package Description Package Option Branding
AD8065AR −40°C to +85°C 8-Lead SOIC_N R-8
AD8065AR-REEL −40°C to +85°C 8-Lead SOIC_N R-8
AD8065AR-REEL7 −40°C to +85°C 8-Lead SOIC_N R-8
AD8065ARZ −40°C to +85°C 8-Lead SOIC_N R-8
AD8065ARZ-REEL −40°C to +85°C 8-Lead SOIC_N R-8
AD8065ARZ-REEL7 −40°C to +85°C 8-Lead SOIC_N R-8
AD8065ART-R2 −40°C to +85°C 5-Lead SOT-23 RJ-5 HRA
AD8065ART-REEL −40°C to +85°C 5-Lead SOT-23 RJ-5 HRA
AD8065ART-REEL7 −40°C to +85°C 5-Lead SOT-23 RJ-5 HRA
AD8065ARTZ-R2 −40°C to +85°C 5-Lead SOT-23 RJ-5 HRA #
AD8065ARTZ-REEL −40°C to +85°C 5-Lead SOT-23 RJ-5 HRA #
AD8065ARTZ-REEL7 −40°C to +85°C 5-Lead SOT-23 RJ-5 HRA #
AD8065WARTZ-REEL7 −40°C to +105°C 5-Lead SOT-23 RJ-5 H2F#
AD8065ART-EBZ Evaluation Board (8-Lead SOIC_N)
AD8065AR-EBZ Evaluation Board (5-Lead SOT-23)
AD8066AR −40°C to +85°C 8-Lead SOIC_N R-8
AD8066AR-REEL7 −40°C to +85°C 8-Lead SOIC_N R-8
AD8066ARZ −40°C to +85°C 8-Lead SOIC_N R-8
AD8066ARZ-RL −40°C to +85°C 8-Lead SOIC_N R-8
AD8066ARZ-R7 −40°C to +85°C 8-Lead SOIC_N R-8
AD8066ARM −40°C to +85°C 8-Lead MSOP RM-8 H1B
AD8066ARM-REEL −40°C to +85°C 8-Lead MSOP RM-8 H1B
AD8066ARM-REEL7 −40°C to +85°C 8-Lead MSOP RM-8 H1B
AD8066ARMZ −40°C to +85°C 8-Lead MSOP RM-8 H7C
AD8066ARMZ-REEL7 −40°C to +85°C 8-Lead MSOP RM-8 H7C
AD8066AR-EBZ Evaluation Board (8-Lead SOIC_N)
AD8066ARM-EBZ Evaluation Board (5-Lead SOT-23)
1 Z = RoHS Compliant Part, # denotes RoHS compliant product may be top or bottom marked.
2 W = Qualified for Automotive Applications.
AUTOMOTIVE PRODUCTS
The AD8065W model is available with controlled manufacturing to support the quality and reliability requirements of automotive
applications. Note that these automotive models may have specifications that differ from the commercial models; therefore, designers
should review the Specifications section of this data sheet carefully. Only the automotive grade products shown are available for use in
automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to
obtain the specific Automotive Reliability reports for these models.
©2002–2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D02916-0-8/10(J)
