LMH6628EP
Enhanced Plastic Dual Wideband, Low Noise, Voltage
Feedback Op Amp
General Description
The National LMH6628EP is a high speed dual op amp that
offers a traditional voltage feedback topology featuring unity
gain stability and slew enhanced circuitry. The
LMH6628EP’s low noise and very low harmonic distortion
combine to form a wide dynamic range op amp that operates
from a single (5V to 12V) or dual (±5V) power supply.
Each of the LMH6628EP’s closely matched channels pro-
vides a 300MHz unity gain bandwidth and low input voltage
noise density (2nV/ ). Low 2nd/3rd harmonic distortion
(−65/−74dBc at 10MHz) make the LMH6628EP a perfect
wide dynamic range amplifier for matched I/Q channels.
With its fast and accurate settling (12ns to 0.1%), the
LMH6628EP is also an excellent choice for wide dynamic
range, anti-aliasing filters to buffer the inputs of hi resolution
analog-to-digital converters. Combining the LMH6628EP’s
two tightly matched amplifiers in a single 8-pin SOIC pack-
age reduces cost and board space for many composite
amplifier applications such as active filters, differential line
drivers/receivers, fast peak detectors and instrumentation
amplifiers.
The LMH6628EP is fabricated using National’s VIP10™
complimentary bipolar process.
To reduce design times and assist in board layout, the
LMH6628EP is supported by an evaluation board
(CLC730036).
ENHANCED PLASTIC
•Extended Temperature Performance of −40˚C to +85˚C
•Baseline Control - Single Fab & Assembly Site
•Process Change Notification (PCN)
•Qualification & Reliability Data
•Solder (PbSn) Lead Finish is standard
•Enhanced Diminishing Manufacturing Sources (DMS)
Support
Features
nWide unity gain bandwidth: 300MHz
nLow noise: 2nV/
nLow Distortion: −65/−74dBc (10MHz)
nSettling time: 12ns to 0.1%
nWide supply voltage range: ±2.5V to ±6V
nHigh output current: ±85mA
nImproved replacement for CLC428
Applications
nHigh speed dual op amp
nLow noise integrators
nSelected Military Applications
nSelected Avionics Applications
Ordering Information
PART NUMBER VID PART NUMBER NS PACKAGE NUMBER (Note 3)
LMH6628MAEP V62/04624-01 M08A
(Notes 1, 2) TBD TBD
Note 1: For the following (Enhanced Plastic) version, check for availability: LMH6628MAXEP. Parts listed with an "X" are provided in Tape & Reel
and parts without an "X" are in Rails.
Note 2: FOR ADDITIONAL ORDERING AND PRODUCT INFORMATION, PLEASE VISIT THE ENHANCED PLASTIC WEB SITE AT: www.national.com/
mil
Note 3: Refer to package details under Physical Dimensions
May 2004
LMH6628EP Enhanced Plastic Dual Wideband, Low Noise, Voltage Feedback Op Amp
© 2005 National Semiconductor Corporation DS200886 www.national.com
Connection Diagram
8-Pin SOIC
20088635
Top View
LMH6628EP Enhanced Plastic
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Absolute Maximum Ratings (Note 4)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 7)
Human Body Model 2kV
Machine Model 200V
Supply Voltage 13.5
Short Circuit Current (Note 6)
Common-Mode Input Voltage V
+
-V
−
Differential Input Voltage V
+
-V
−
Maximum Junction Temperature +150˚C
Storage Temperature Range −65˚C to +150˚C
Lead Temperature (soldering 10 sec) +300˚C
Operating Ratings (Note 4)
Thermal Resistance (Note 8)
Package (θ
JC
)(θ
JA
)
SOIC 65˚C/W 145˚C/W
Temperature Range −40˚C to +85˚C
Nominal Supply Voltage ±2.5V to ±6V
Electrical Characteristics (Note 5)
V
CC
=±5V, A
V
= +2V/V, R
F
= 100Ω,R
G
= 100Ω,R
L
= 100Ω; unless otherwise specified. Boldface limits apply at the
temperature extremes.
Symbol Parameter Conditions Min Typ Max Units
Frequency Domain Response
GB Gain Bandwidth Product V
O
<0.5V
PP
200 MHz
SSBW -3dB Bandwidth, A
V
=+1 V
O
<0.5V
PP
180 300 MHz
SSBW -3dB Bandwidth, A
V
=+2 V
O
<0.5V
PP
100 MHz
GFL Gain Flatness V
O
<0.5V
PP
GFP Peaking DC to 200MHz 0.0 dB
GFR Rolloff DC to 20MHz .1 dB
LPD Linear Phase Deviation DC to 20MHz .1 deg
Time Domain Response
TR Rise and Fall Time 1V Step 4 ns
TS Settling Time 2V Step to 0.1% 12 ns
OS Overshoot 1V Step 1 %
SR Slew Rate 4V Step 300 550 V/µs
Distortion And Noise Response
HD2 2nd Harmonic Distortion 1V
PP
, 10MHz −65 dBc
HD3 3rd Harmonic Distortion 1V
PP
, 10MHz −74 dBc
Equivalent Input Noise
V
N
Voltage 1MHz to 100MHz 2 nV/
I
N
Current 1MHz to 100MHz 2 pA/
XTLKA Crosstalk Input Referred, 10MHz −62 dB
Static, DC Performance
G
OL
Open-Loop Gain 56
53
63 dB
V
IO
Input Offset Voltage ±.5 ±2
±2.6
mV
DV
IO
Average Drift 5 µV/˚C
I
BN
Input Bias Current ±.7 ±20
±30
µA
DI
BN
Average Drift 150 nA/˚C
I
OS
Input Offset Current 0.3 ±6µA
I
OSD
Average Drift 5 nA/˚C
PSRR Power Supply Rejection Ratio 60
46
70 dB
CMRR Common-Mode Rejection Ratio 57
54
62 dB
I
CC
Supply Current Per Channel, R
L
=∞7.5
7.0
912
12.5
mA
LMH6628EP Enhanced Plastic
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Electrical Characteristics (Note 5) (Continued)
V
CC
=±5V, A
V
= +2V/V, R
F
= 100Ω,R
G
= 100Ω,R
L
= 100Ω; unless otherwise specified. Boldface limits apply at the
temperature extremes.
Symbol Parameter Conditions Min Typ Max Units
Miscellaneous Performance
R
IN
Input Resistance Common-Mode 500 kΩ
Differential-Mode 200 kΩ
C
IN
Input Capacitance Common-Mode 1.5 pF
Differential-Mode 1.5 pF
R
OUT
Output Resistance Closed-Loop .1 Ω
V
O
Output Voltage Range R
L
=∞±3.8 V
V
OL
R
L
= 100Ω±3.2
±3.1
±3.5 V
CMIR Input Voltage Range Common- Mode ±3.7 V
I
O
Output Current ±50 ±85 mA
Note 4: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but specific performance is not guaranteed. For guaranteed specifications, see the Electrical Characteristics tables.
Note 5: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of
the device such that TJ=T
A. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self heating where TJ>TA.
See Note 6 for information on temperature de-rating of this device." Min/Max ratings are based on product characterization and simulation. Individual parameters
are tested as noted.
Note 6: Output is short circuit protected to ground, however maximum reliability is obtained if output current does not exceed 160mA.
Note 7: Human body model, 1.5kΩin series with 100pF. Machine model, 0ΩIn series with 200pF.
Note 8: The maximum power dissipation is a function of TJ(MAX),θJA and TA. The maximum allowable power dissipation at any ambient temperature is
PD=(T
J(MAX)-TA)/ θJA. All numbers apply for packages soldered directly onto a PC board.
LMH6628EP Enhanced Plastic
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Typical Performance Characteristics (T
A
= +25˚, A
V
= +2, V
CC
=±5V, R
f
=100Ω,R
L
= 100Ω, un-
less specified)
Non-Inverting Frequency Response Inverting Frequency Response
20088613 20088615
Frequency Response vs. Load Resistance Frequency Response vs. Output Amplitude
20088625 20088610
Frequency Response vs. Capacitive Load Gain Flatness & Linear Phase
20088616
20088624
LMH6628EP Enhanced Plastic
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Typical Performance Characteristics (T
A
= +25˚, A
V
= +2, V
CC
=±5V, R
f
=100Ω,R
L
= 100Ω, unless
specified) (Continued)
Channel Matching Channel to Channel Crosstalk
20088614 20088609
Pulse Response (V
O
= 2V) Pulse Response (V
O
= 100mV)
20088611 20088612
2nd Harmonic Distortion vs. Output Voltage 3rd Harmonic Distortion vs. Output Voltage
20088607 20088608
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Typical Performance Characteristics (T
A
= +25˚, A
V
= +2, V
CC
=±5V, R
f
=100Ω,R
L
= 100Ω, unless
specified) (Continued)
2nd & 3rd Harmonic Distortion vs. Frequency PSRR and CMRR (±5V)
20088617 20088622
PSRR and CMRR (±2.5V) Closed Loop Output Resistance (±2.5V)
20088623 20088618
Closed Loop Output Resistance (±5V) Open Loop Gain & Phase (±2.5V)
20088619 20088621
LMH6628EP Enhanced Plastic
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Typical Performance Characteristics (T
A
= +25˚, A
V
= +2, V
CC
=±5V, R
f
=100Ω,R
L
= 100Ω, unless
specified) (Continued)
Open Loop Gain & Phase (±5V) Recommended R
S
vs. C
L
20088620
20088626
DC Errors vs. Temperature Maximum V
O
vs. R
L
20088646 20088645
2-Tone, 3rd Order Intermodulation Intercept Voltage & Current Noise vs. Frequency
20088644 20088647
LMH6628EP Enhanced Plastic
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Typical Performance Characteristics (T
A
= +25˚, A
V
= +2, V
CC
=±5V, R
f
=100Ω,R
L
= 100Ω, unless
specified) (Continued)
Settling Time vs. Accuracy
20088648
Application Section
LOW NOISE DESIGN
Ultimate low noise performance from circuit designs using
the LMH6628EP requires the proper selection of external
resistors. By selecting appropriate low valued resistors for
R
F
and R
G
, amplifier circuits using the LMH6628EP can
achieve output noise that is approximately the equivalent
voltage input noise of 2nV/ multiplied by the desired
gain (A
V
).
DC BIAS CURRENTS AND OFFSET VOLTAGES
Cancellation of the output offset voltage due to input bias
currents is possible with the LMH6628EP. This is done by
making the resistance seen from the inverting and non-
inverting inputs equal. Once done, the residual output offset
voltage will be the input offset voltage (V
OS
) multiplied by the
desired gain (A
V
). National Application Note OA-7 offers
several solutions to further reduce the output offset.
OUTPUT AND SUPPLY CONSIDERATIONS
With ±5V supplies, the LMH6628EP is capable of a typical
output swing of ±3.8V under a no-load condition. Additional
output swing is possible with slightly higher supply voltages.
For loads of less than 50Ω, the output swing will be limited by
the LMH6628EP’s output current capability, typically 85mA.
Output settling time when driving capacitive loads can be
improved by the use of a series output resistor. See the plot
labeled "R
S
vs. C
L
" in the Typical Performance section.
LAYOUT
Proper power supply bypassing is critical to insure good high
frequency performance and low noise. De-coupling capaci-
tors of 0.1µF should be placed as close as possible to the
power supply pins. The use of surface mounted capacitors is
recommended due to their low series inductance.
A good high frequency layout will keep power supply and
ground traces away from the inverting input and output pins.
Parasitic capacitance from these nodes to ground causes
frequency response peaking and possible circuit oscillation.
See OA-15 for more information. National suggests the
730036 (SOIC) dual op amp evaluation board as a guide for
high frequency layout and as an aid in device evaluation.
ANALOG DELAY CIRCUIT (ALL-PASS NETWORK)
The circuit in Figure 1 implements an all-pass network using
the LMH6628EP. A wide bandwidth buffer (LM7121) drives
the circuit and provides a high input impedance for the
source. As shown in Figure 2, the circuit provides a 13.1ns
delay (with R = 40.2Ω, C = 47pF). R
F
and R
G
should be of
equal and low value for parasitic insensitive operation.
20088601
FIGURE 1.
20088602
FIGURE 2. Delay Circuit Response to 0.5V Pulse
LMH6628EP Enhanced Plastic
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Application Section (Continued)
The circuit gain is +1 and the delay is determined by the
following equations.
(1)
Td
df
d=1
360
φ;
(2)
where T
d
is the delay of the op amp at A
V
= +1.
The LMH6628EP provides a typical delay of 2.8ns at its
−3dB point.
FULL DUPLEX DIGITAL OR ANALOG TRANSMISSION
Simultaneous transmission and reception of analog or digital
signals over a single coaxial cable or twisted-pair line can
reduce cabling requirements. The LMH6628EP’s wide band-
width and high common-mode rejection in a differential am-
plifier configuration allows full duplex transmission of video,
telephone, control and audio signals.
In the circuit shown in Figure 3, one of the LMH6628EP’s
amps is used as a "driver" and the other as a difference
"receiver" amplifier. The output impedance of the "driver" is
essentially zero. The two R’s are chosen to match the char-
acteristic impedance of the transmission line. The "driver" op
amp gain can be selected for unity or greater.
Receiver amplifier A
2
(B
2
) is connected across R and forms
differential amplifier for the signals transmitted by driver A
2
(B
2
). If R
F
equals R
G
, receiver A
2
(B
1
) will then reject the
signals from driver A
1
(B
1
) and pass the signals from driver
B
1
(A
1
).
The output of the receiver amplifier will be:
(3)
Care must be given to layout and component placement to
maintain a high frequency common-mode rejection. The plot
of Figure 4 shows the simultaneous reception of signals
transmitted at 1MHz and 10MHz.
POSITIVE PEAK DETECTOR
The LMH6628EP’s dual amplifiers can be used to implement
a unity-gain peak detector circuit as shown in Figure 5.
The acquisition speed of this circuit is limited by the dynamic
resistance of the diode when charging C
hold
. A plot of the
circuit’s performance is shown in Figure 6 with a 1MHz
sinusoidal input.
20088603
FIGURE 3.
20088631
FIGURE 4.
20088605
FIGURE 5.
LMH6628EP Enhanced Plastic
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Application Section (Continued)
A current source, built around Q1, provides the necessary
bias current for the second amplifier and prevents saturation
when power is applied. The resistor, R, closes the loop while
diode D2 prevents negative saturation when V
IN
is less than
V
C
. A MOS-type switch (not shown) can be used to reset the
capacitor’s voltage.
The maximum speed of detection is limited by the delay of
the op amps and the diodes. The use of Schottky diodes will
provide faster response.
ADJUSTABLE OR BANDPASS EQUALIZER
A "boost" equalizer can be made with the LMH6628EP by
summing a bandpass response with the input signal, as
shown in Figure 7.
The overall transfer function is shown in Eq. 5.
(4)
To build a boost circuit, use the design equations Eq. 6 and
Eq. 7.
(5)
(6)
Select R
2
and C using Eq. 6. Use reasonable values for high
frequency circuits - R
2
between 10Ωand 5kΩ, C between
10pF and 2000pF. Use Eq. 7 to determine the parallel com-
bination of R
a
and R
b
. Select R
a
and R
b
by either the 10Ωto
5kΩcriteria or by other requirements based on the imped-
ance V
in
is capable of driving. Finish the design by determin-
ing the value of K from Eq. 8.
(7)
Figure 8 shows an example of the response of the circuit of
Figure 9, where f
o
is 2.3MHz. The component values are as
follows: R
a
=2.1kΩ,R
b
= 68.5Ω,R
2
= 4.22kΩ,R=500Ω,KR
=50Ω, C = 120pF.
20088637
FIGURE 6.
20088606
FIGURE 7.
20088643
FIGURE 8.
LMH6628EP Enhanced Plastic
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Physical Dimensions inches (millimeters)
unless otherwise noted
8-Pin SOIC
NS Package Number M08A
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
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LMH6628EP Enhanced Plastic Dual Wideband, Low Noise, Voltage Feedback Op Amp
