1
LT1207
Dual 250mA/60MHz
Current Feedback Amplifier
S
FEATURE
■
250mA Minimum Output Drive Current
■
60MHz Bandwidth, A
V
= 2, R
L
= 100Ω
■
900V/µs Slew Rate, A
V
= 2, R
L
= 50Ω
■
0.02% Differential Gain, A
V
= 2, R
L
= 30Ω
■
0.17° Differential Phase, A
V
= 2, R
L
= 30Ω
■
High Input Impedance: 10MΩ
■
Shutdown Mode: I
S
< 200µA per Amplifier
■
Stable with C
L
= 10,000pF
APPLICATIO S
U
■
ADSL/HDSL Drivers
■
Video Amplifiers
■
Cable Drivers
■
RGB Amplifiers
■
Test Equipment Amplifiers
■
Buffers
The LT
®
1207 is a dual version of the LT1206 high speed
current feedback amplifier. Like the LT1206, each CFA in
the dual has excellent video characteristics: 60MHz band-
width, 250mA minimum output drive current, 400V/µs
minimum slew rate, low differential gain (0.02% typ) and
low differential phase (0.17° typ). The LT1207 includes a
pin for an optional compensation network which stabi-
lizes the amplifier for heavy capacitive loads. Both ampli-
fiers have thermal and current limit circuits which protect
against fault conditions. These capabilities make the LT1207
well suited for driving difficult loads such as cables in video
or digital communication systems.
Operation is fully specified from ±5V to ±15V supplies.
Supply current is typically 20mA per amplifier. Two
micropower shutdown controls place each amplifier in a
high impedance low current mode, dropping supply
current to 200µA per amplifier. For reduced bandwidth
applications, supply current can be lowered by adding a
resistor in series with the Shutdown pin.
The LT1207 is manufactured on Linear Technology's
complementary bipolar process and is available in a low
thermal resistance 16-lead SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
U
D
U
ESCRIPTIO
HDSL Driver
–
+
1/2 LT1207
+
–
240Ω
720Ω
720Ω
720Ω
15k
15k
V
IN
+
0.1µF*
2.2µF**
5V
+
0.1µF*
2.2µF**
–5V
62Ω
62Ω
L1
1207 • TA01
1/2 LT1207
SHDN A
SHDN B CERAMIC
TANTALUM
L1 =TRANSPOWER SMPT–308
OR SIMILAR DEVICE
*
**
2
LT1207
A
U
G
W
A
W
U
W
ARBSOLUTEXI T
I
S
WU
U
PACKAGE/ORDER I FOR ATIO
Supply Voltage ..................................................... ±18V
Input Current per Amplifier ............................... ±15mA
Output Short-Circuit Duration (Note 1)....... Continuous
Specified Temperature Range (Note 2)...... 0°C to 70°C
Operating Temperature Range ............... –40°C to 85°C
Junction Temperature......................................... 150°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LT1207CS
Consult factory for Industrial and Military grade parts.
θ
JA
= 40°C/W (NOTE 3)
VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, VSHDN A = 0V, VSHDN B = 0V, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
OS
Input Offset Voltage T
A
= 25°C±3±10 mV
●±15 mV
Input Offset Voltage Drift ●10 µV/°C
I
IN+
Noninverting Input Current T
A
= 25°C±2±5µA
●±20 µA
I
IN–
Inverting Input Current T
A
= 25°C±10 ±60 µA
●±100 µA
e
n
Input Noise Voltage Density f = 10kHz, R
F
= 1k, R
G
= 10Ω, R
S
= 0Ω3.6 nV/√Hz
+i
n
Input Noise Current Density f = 10kHz, R
F
= 1k, R
G
= 10Ω, R
S
= 10k 2 pA/√Hz
–i
n
Input Noise Current Density f = 10kHz, R
F
= 1k, R
G
= 10Ω, R
S
= 10k 30 pA/√Hz
R
IN
Input Resistance V
IN
= ±12V, V
S
= ±15V ●1.5 10 MΩ
V
IN
= ±2V, V
S
= ±5V ●0.5 5 MΩ
C
IN
Input Capacitance V
S
= ±15V 2 pF
Input Voltage Range V
S
= ±15V ●±12 ±13.5 V
V
S
= ±5V ●±2 ±3.5 V
CMRR Common Mode Rejection Ratio V
S
= ±15V, V
CM
= ±12V ●55 62 dB
V
S
= ±5V, V
CM
= ±2V ●50 60 dB
Inverting Input Current V
S
= ±15V, V
CM
= ±12V ●0.1 10 µA/V
Common Mode Rejection V
S
= ±5V, V
CM
= ±2V ●0.1 10 µA/V
PSRR Power Supply Rejection Ratio V
S
= ±5V to ±15V ●60 77 dB
TOP VIEW
S PACKAGE
16-LEAD PLASTIC SO
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
+
–IN A
+IN A
SHDN A
–IN B
+IN B
SHDN B
V
+
V
+
OUT A
V
–
A
COMP A
OUT B
V
–
B
COMP B
V
+
3
LT1207
VCM = 0, ±5V ≤ VS ≤ ±15V, pulse tested, VSHDN A = 0V, VSHDN B = 0V, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Noninverting Input Current V
S
= ±5V to ±15V ●30 500 nA/V
Power Supply Rejection
Inverting Input Current V
S
= ±5V to ±15V ●0.7 5 µA/V
Power Supply Rejection
A
V
Large-Signal Voltage Gain V
S
= ±15V, V
OUT
= ±10V, R
L
= 50Ω●55 71 dB
V
S
= ±5V, V
OUT
= ±2V, R
L
= 25Ω●55 68 dB
R
OL
Transresistance, ∆V
OUT
/∆I
IN–
V
S
= ±15V, V
OUT
= ±10V, R
L
= 50Ω●100 260 kΩ
V
S
= ±5V, V
OUT
= ±2V, R
L
= 25Ω●75 200 kΩ
V
OUT
Maximum Output Voltage Swing V
S
= ±15V, R
L
= 50Ω, T
A
= 25°C±11.5 ±12.5 V
●±10.0 V
V
S
= ±5V, R
L
= 25Ω, T
A
= 25°C±2.5 ±3.0 V
●±2.0 V
I
OUT
Maximum Output Current R
L
= 1Ω●250 500 1200 mA
I
S
Supply Current per Amplifier V
S
= ±15V, V
SHDN
= 0V, T
A
= 25°C2030mA
●35 mA
Supply Current per Amplifier, V
S
= ±15V, T
A
= 25°C1217mA
R
SHDN
= 51k (Note 4)
Positive Supply Current V
S
= ±15V, V
SHDN A
= 15V, V
SHDN B
= 15V ●200 µA
per Amplifier, Shutdown
Output Leakage Current, Shutdown V
S
= ±15V, V
SHDN
= 15V, V
OUT
= 0V ●10 µA
SR Slew Rate (Note 5) A
V
= 2, T
A
= 25°C 400 900 V/µs
Differential Gain (Note 6) V
S
= ±15V, R
F
= 560Ω, R
G
= 560Ω, R
L
= 30Ω0.02 %
Differential Phase (Note 6) V
S
= ±15V, R
F
= 560Ω, R
G
= 560Ω, R
L
= 30Ω0.17 DEG
BW Small-Signal Bandwidth V
S
= ±15V, Peaking ≤ 0.5dB 60 MHz
R
F
= R
G
= 620Ω, R
L
= 100Ω
V
S
= ±15V, Peaking ≤ 0.5dB 52 MHz
R
F
= R
G
= 649Ω, R
L
= 50Ω
V
S
= ±15V, Peaking ≤ 0.5dB 43 MHz
R
F
= R
G
= 698Ω, R
L
= 30Ω
V
S
= ±15V, Peaking ≤ 0.5dB 27 MHz
R
F
= R
G
= 825Ω, R
L
= 10Ω
Note 3: Thermal resistance θ
JA
varies from 40°C/W to 60°C/W depending
upon the amount of PC board metal attached to the device. θ
JA
is specified
for a 2500mm
2
test board covered with 2oz copper on both sides.
Note 4: R
SHDN
is connected between the Shutdown pin and ground.
Note 5: Slew rate is measured at ±5V on a ±10V output signal while
operating on ±15V supplies with R
F
= 1.5k, R
G
= 1.5k and R
L
= 400Ω.
Note 6: NTSC composite video with an output level of 2V.
The ● denotes specifications which apply for 0°C ≤ T
A
≤ 70°C.
Note 1: Applies to short circuits to ground only. A short circuit between
the output and either supply may permanently damage the part when
operated on supplies greater than ±10V.
Note 2: Commercial grade parts are designed to operate over the
temperature range of –40°C to 85°C but are neither tested nor guaranteed
beyond 0°C to 70°C. Industrial grade parts tested over –40°C to 85°C are
available on special request. Consult factory.
4
LT1207
S ALL-SIG AL BA DWIDTH
WU
U
I
S
= 20mA per Amplifier Typical, Peaking ≤ 0.1dB
IS = 10mA per Amplifier Typical, Peaking ≤ 0.1dB
IS = 5mA per Amplifier Typical, Peaking ≤ 0.1dB
–3dB BW –0.1dB BW
A
V
R
L
R
F
R
G
(MHz) (MHz)
V
S
= ±5V, R
SHDN
= 22.1k
–1 150 604 604 21 10.5
30 715 715 14.6 7.4
10 681 681 10.5 6.0
1 150 768 – 20 9.6
30 866 – 14.1 6.7
10 825 – 9.8 5.1
2 150 634 634 20 9.6
30 750 750 14.1 7.2
10 732 732 9.6 5.1
10 150 100 11.1 16.2 5.8
30 100 11.1 13.4 7.0
10 100 11.1 9.5 4.7
–3dB BW –0.1dB BW
A
V
R
L
R
F
R
G
(MHz) (MHz)
V
S
= ±15V, R
SHDN
= 121k
–1 150 619 619 25 12.5
30 787 787 15.8 8.5
10 825 825 10.5 5.4
1 150 845 – 23 10.6
30 1k – 15.3 7.6
10 1k – 10 5.2
2 150 681 681 23 10.2
30 845 845 15 7.7
10 866 866 10 5.4
10 150 100 11.1 15.9 4.5
30 100 11.1 13.6 6
10 100 11.1 9.6 4.5
–3dB BW –0.1dB BW
A
V
R
L
R
F
R
G
(MHz) (MHz)
V
S
= ±5V, R
SHDN
= 0Ω
–1 150 562 562 48 21.4
30 649 649 34 17
10 732 732 22 12.5
1 150 619 – 54 22.3
30 715 – 36 17.5
10 806 – 22.4 11.5
2 150 576 576 48 20.7
30 649 649 35 18.1
10 750 750 22.4 11.7
10 150 442 48.7 40 19.2
30 511 56.2 31 16.5
10 649 71.5 20 10.2
–3dB BW –0.1dB BW
A
V
R
L
R
F
R
G
(MHz) (MHz)
V
S
= ±15V, R
SHDN
= 0Ω
–1 150 681 681 50 19.2
30 768 768 35 17
10 887 887 24 12.3
1 150 768 – 66 22.4
30 909 – 37 17.5
10 1k – 23 12
2 150 665 665 55 23
30 787 787 36 18.5
10 931 931 22.5 11.8
10 150 487 536 44 20.7
30 590 64.9 33 17.5
10 768 84.5 20.7 10.8
–3dB BW –0.1dB BW
A
V
R
L
R
F
R
G
(MHz) (MHz)
V
S
= ±5V, R
SHDN
= 10.2k
–1 150 576 576 35 17
30 681 681 25 12.5
10 750 750 16.4 8.7
1 150 665 – 37 17.5
30 768 – 25 12.6
10 845 – 16.5 8.2
2 150 590 590 35 16.8
30 681 681 25 13.4
10 768 768 16.2 8.1
10 150 301 33.2 31 15.6
30 392 43.2 23 11.9
10 499 54.9 15 7.8
–3dB BW –0.1dB BW
A
V
R
L
R
F
R
G
(MHz) (MHz)
V
S
= ±15V, R
SHDN
= 60.4k
–1 150 634 634 41 19.1
30 768 768 26.5 14
10 866 866 17 9.4
1 150 768 – 44 18.8
30 909 – 28 14.4
10 1k – 16.8 8.3
2 150 649 649 40 18.5
30 787 787 27 14.1
10 931 931 16.5 8.1
10 150 301 33.2 33 15.6
30 402 44.2 25 13.3
10 590 64.9 15.3 7.4
5
LT1207
TYPICAL PERFOR A CE CHARACTERISTICS
WU
Bandwidth and Feedback Resistance
vs Capacitive Load for 0.5dB Peak
Bandwidth vs Supply Voltage
Bandwidth vs Supply Voltage
Bandwidth vs Supply Voltage
Spot Noise Voltage and Current
vs Frequency
Bandwidth and Feedback Resistance
vs Capacitive Load for 5dB Peak
4
0
10
30
40
50
100
70
812
20
80
90
60
610
14 16 18
SUPPLY VOLTAGE (±V)
–3dB BANDWIDTH (MHz)
LT1207 • TPC01
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
R
F
= 470Ω
R
F
= 560ΩR
F
= 680Ω
R
F
= 750Ω
R
F
= 1k
R
F
= 1.5k
A
V
= 2
R
L
= 100Ω
4
0
20
50
812
10
40
30
610
14 16 18
SUPPLY VOLTAGE (±V)
–3dB BANDWIDTH (MHz)
LT1207 • TPC02
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
R
F
= 560Ω
R
F
= 1k
R
F
= 2k
R
F
= 750Ω
A
V
= 2
R
L
= 10Ω
4
0
10
30
40
50
100
70
812
20
80
90
60
610
14 16 18
SUPPLY VOLTAGE (±V)
–3dB BANDWIDTH (MHz)
LT1207 • TPC04
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
R
F
= 470Ω
R
F
= 1.5k
R
F
= 330Ω
R
F
= 680Ω
R
F
=390Ω
A
V
= 10
R
L
= 100Ω
4
0
20
50
812
10
40
30
610
14 16 18
SUPPLY VOLTAGE (±V)
–3dB BANDWIDTH (MHz)
LT1207 • TPC05
PEAKING ≤ 0.5dB
PEAKING ≤ 5dB
R
F
= 560Ω
R
F
= 1k
R
F
= 1.5k
R
F
= 680Ω
A
V
= 10
R
L
= 10Ω
CAPACITIVE LOAD (pF)
FEEDBACK RESISTOR (Ω)
1
LT1207 • TPC06
10 100 1k 10k
0
–3dB BANDWIDTH (MHz)
1k
10k
0
100
10
100
1
FEEDBACK RESISTOR
BANDWIDTH
A
V
= +2
R
L
= ∞
V
S
= ±15V
C
COMP
= 0.01µF
FREQUENCY (Hz)
10
1
10
100
100 100k
LT1207 • TPC09
1k 10k
SPOT NOISE (nV/√Hz OR pA/√Hz)
i
n
e
n
–i
n
Bandwidth vs Supply Voltage
CAPACITIVE LOAD (pF)
1
100
FEEDBACK RESISTOR (Ω)
1k
10k
100 10000
LT1207 • TPC03
10 1000
BANDWIDTH
FEEDBACK RESISTOR
A
V
= 2
R
L
=
∞
V
S
= ±15V
C
COMP
= 0.01µF1
10
100
–3dB BANDWIDTH (MHz)
Differential Phase
vs Supply Voltage
Differential Gain
vs Supply Voltage
SUPPLY VOLTAGE (±V)
5
DIFFERENTIAL PHASE (DEG)
0.30
0.40
0.50
13
LT1207 • TPC07
0.20
0.10
07911 15
R
F
= R
G
= 560Ω
A
V
= 2
N PACKAGE
R
L
= 15Ω
R
L
= 50Ω
R
L
= 30Ω
R
L
= 150Ω
SUPPLY VOLTAGE (±V)
5
DIFFERENTIAL GAIN (%)
0.06
0.08
0.10
13
LT1207 • TPC08
0.04
0.02
07911 15
R
F
= R
G
= 560Ω
A
V
= 2
N PACKAGE
R
L
= 15Ω
R
L
= 30Ω
R
L
= 150Ω
R
L
= 50Ω
6
LT1207
Supply Current vs
Ambient Temperature, VS = ±15V
Output Short-Circuit Current
vs Junction Temperature
Supply Current vs Large-Signal
Output Frequency (No Load)
TYPICAL PERFOR A CE CHARACTERISTICS
WU
Supply Current
vs Shutdown Pin Current Input Common Mode Limit
vs Junction Temperature
Output Saturation Voltage
vs Junction Temperature Power Supply Rejection Ratio
vs Frequency
Supply Current vs
Ambient Temperature, VS = ±5V
4
10
12
16
18
22
812
14
24
20
610
14 16 18
SUPPLY VOLTAGE (±V)
SUPPLY CURRENT PER AMPLIFIER (mA)
LT1207 • TPC10
T
J
= –40˚C
T
J
= 25˚C
T
J
= 85˚C
T
J
= 125˚C
V
SHDN
= 0V
TEMPERATURE (°C)
–50
0
SUPPLY CURRENT PER AMPLIFIER (mA)
10
25
050 75
LT1207 • TPC11
5
20
15
–25 25 100 125
A
V
= 1
R
L
=
∞
R
SD
= 0Ω
R
SD
= 10.2k
R
SD
= 22.1k
TEMPERATURE (°C)
–50
0
SUPPLY CURRENT PER AMPLIFIER (mA)
10
25
050 75
LT1207 • TPC12
5
20
15
–25 25 100 125
A
V
= 1
R
L
=
∞
R
SD
= 0Ω
R
SD
= 60.4k
R
SD
= 121k
TEMPERATURE (°C)
–50
V
–
COMMON MODE RANGE (V)
0.5
1.5
2.0
–2.0
75
V
+
LT1207 • TPC14
1.0
0 125
–1.5
–1.0
– 0.5
50
–25 100
25
SHUTDOWN PIN CURRENT (µA)
0
SUPPLY CURRENT PER AMPLIFIER (mA)
12
16
20
400
LT1207 • TPC13
8
4
0100 200 300 500
10
14
18
6
2
V
S
= ±15V
TEMPERATURE (°C)
–50
0.7
0.8
1.0
25 75
LT1207 • TPC15
0.6
0.5
–25 0 50 100 125
0.4
0.3
0.9
OUTPUT SHORT-CIRCUIT CURRENT (A)
SOURCING
SINKING
TEMPERATURE (°C)
–50
V–
OUTPUT SATURATION VOLTAGE (V)
1
3
4
–4
75
V+
LT1207 • TPC16
2
0 125
–3
–2
–1
50
–25 100
25
VS = ±15V RL = 2k
RL = 50Ω
RL = 50Ω
RL = 2k
FREQUENCY (Hz)
20
POWER SUPPLY REJECTION (dB)
40
60
70
10k 1M 10M 100M
LT1207 • TPC17
0100k
50
30
10
R
L
= 50Ω
V
S
= ±15V
R
F
= R
G
= 1k
NEGATIVE
POSITIVE
Supply Current vs Supply Voltage
FREQUENCY (Hz)
10k
SUPPLY CURRENT PER AMPLIFIER (mA)
40
50
60
100k 1M 10M
LT1207 • TPC18
30
20
10
A
V
= 2
R
L
=
∞
V
S
= ±15V
V
OUT
= 20V
P-P
7
LT1207
2nd and 3rd Harmonic Distortion
vs Frequency
Output Impedance vs Frequency
TYPICAL PERFOR A CE CHARACTERISTICS
WU
Output Impedance in Shutdown
vs Frequency
FREQUENCY (Hz)
0.1
OUTPUT IMPEDANCE (Ω)
1
10
100
100k 10M 100M
LT1207 • TPC19
0.01 1M
VS = ±15V
IO = 0mA
RSHDN = 121k
RSHDN = 0Ω
FREQUENCY (Hz)
100
OUTPUT IMPEDANCE (Ω)
1k
10k
100k
100k 10M 100M
LT1207 • TPC20
10 1M
AV = 1
RF = 1k
VS = ±15V
FREQUENCY (MHz)
1
–90
DISTORTION (dBc)
–80
–70
–60
–50
–30
310
LT1207 • TPC21
–40
2456789
V
S
= ±15V
V
O
= 2V
P-P
2nd
3rd
R
L
= 10Ω
2nd
3rd
R
L
= 30Ω
Test Circuit for 3rd Order Intercept3rd Order Intercept vs Frequency
FREQUENCY (MHz)
0
10
3rd ORDER INTERCEPT (dBm)
20
30
40
50
60
510 15 20
LT1207 • TPC22
25 30
VS = ±15V
RL = 50Ω
RF = 590Ω
RG = 64.9Ω
–
+
50Ω
1/2 LT1207
LT1207 • TPC23
65Ω
590Ω
P
O
MEASURE INTERCEPT AT P
O
8
LT1207
SI PLIFIED SCHE ATIC
WW
LT1207 • SS
V
–
OUTPUT
V
+
50Ω
D2
D1
V
–
V
+
V
+
V
–
C
C
R
C
COMP–IN+IN
SHUTDOWN
1.25k
TO ALL
CURRENT
SOURCES
Q11
Q15
Q9
Q6
Q5
Q2
Q1Q18
Q17
Q3
Q4
Q7
Q8
Q12
Q16 Q14
Q13
Q10
1/2 LT1207 CURRENT FEEDBACK AMPLIFIER
U
S
A
O
PPLICATI
WU
U
I FOR ATIO
The LT1207 is a dual current feedback amplifier with high
output current drive capability. The device is stable with
large capacitive loads and can easily supply the high
currents required by capacitive loads. The amplifier will
drive low impedance loads such as cables with excellent
linearity at high frequencies.
Feedback Resistor Selection
The optimum value for the feedback resistors is a function
of the operating conditions of the device, the load imped-
ance and the desired flatness of response. The Typical AC
Performance tables give the values which result in the
highest 0.1dB and 0.5dB bandwidths for various resistive
loads and operating conditions. If this level of flatness is
not required, a higher bandwidth can be obtained by use
of a lower feedback resistor. The characteristic curves of
Bandwidth vs Supply Voltage indicate feedback resistors
for peaking up to 5dB. These curves use a solid line when
the response has less than 0.5dB of peaking and a dashed
line when the response has 0.5dB to 5dB of peaking. The
curves stop where the response has more than 5dB of
peaking.
For resistive loads, the COMP pin should be left open (see
section on capacitive loads).
Capacitive Loads
Each amplifier in the LT1207 includes an optional com-
pensation network for driving capacitive loads. This net-
work eliminates most of the output stage peaking associ-
ated with capacitive loads, allowing the frequency re-
sponse to be flattened. Figure 1 shows the effect of the
network on a 200pF load. Without the optional compensa-
tion, there is a 5dB peak at 40MHz caused by the effect of
the capacitance on the output stage. Adding a 0.01µF
bypass capacitor between the output and the COMP pins
connects the compensation and completely eliminates the
peaking. A lower value feedback resistor can now be used,
resulting in a response which is flat to 0.35dB to 30MHz.
9
LT1207
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FREQUENCY (MHz)
1
–8
VOLTAGE GAIN (dB)
–4
0
4
8
10 100
LT1207 • F01
–6
–2
2
6
10
12 V
S
= ±15V
R
F
= 1.2k
COMPENSATION
R
F
= 2k
NO COMPENSATION
R
F
= 2k
COMPENSATION
Figure 1.
The network has the greatest effect for C
L
in the range of
0pF to 1000pF. The graph of Maximum Capacitive Load vs
Feedback Resistor can be used to select the appropriate
value of the feedback resistor. The values shown are for
0.5dB and 5dB peaking at a gain of 2 with no resistive load.
This is a worst-case condition, as the amplifier is more stable
at higher gains and with some resistive load in parallel with
the capacitance. Also shown is the –3dB bandwidth with the
suggested feedback resistor vs the load capacitance.
Although the optional compensation works well with
capacitive loads, it simply reduces the bandwidth when it
is connected with resistive loads. For instance, with a 30Ω
load, the bandwidth drops from 55MHz to 35MHz when
the compensation is connected. Hence, the compensation
was made optional. To disconnect the optional compensa-
tion, leave the COMP pin open.
Shutdown/Current Set
If the shutdown feature is not used, the Shutdown pins
must be connected to ground or V
–
.
Each amplifier has a separate Shutdown pin which can be
used to either turn off the amplifier, which reduces the
amplifier supply current to less than 200µA, or to control
the supply current in normal operation.
The supply current in each amplifier is controlled by the
current flowing out of the Shutdown pin. When the Shut-
down pin is open or driven to the positive supply, the
amplifier is shut down. In the shutdown mode, the output
looks like a 40pF capacitor and the supply current is
typically 100µA. Each Shutdown pin is referenced to the
positive supply through an internal bias circuit (see the
Simplified Schematic). An easy way to force shutdown is
to use open drain (collector) logic. The circuit shown in
Figure 2 uses a 74C904 buffer to interface between 5V
logic and the LT1207. The switching time between the
active and shutdown states is less than 1µs.
A 24k pull-up
resistor speeds up the turn-off time and insures that the
amplifier is completely turned off. Because the pin is
referenced to the positive supply, the logic used should
have a breakdown voltage of greater than the positive
supply voltage. No other circuitry is necessary as the
internal circuit limits the Shutdown pin current to about
500µA. Figure 3 shows the resulting waveforms.
Figure 2. Shutdown Interface
–
+
1/2 LT1207
SHDN
15V
–15V R
F
R
G
V
IN
5V 24k
ENABLE
V
OUT
LT1207 • F02
15V
74C906
For applications where the full bandwidth of the amplifier
is not required, the quiescent current may be reduced by
connecting a resistor from the Shutdown pin to ground.
Figure 3. Shutdown Operation
LT1207 • F3
A
V
= 1
R
F
= 825Ω
R
L
= 50Ω
R
PU
= 24k
V
IN
= 1V
P-P
ENABLE V
OUT
10
LT1207
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and for higher gains in the noninverting mode, the signal
amplitude on the input pins is small and the overall slew
rate is that of the output stage. The input stage slew rate
is related to the quiescent current and will be reduced as
the supply current is reduced. The output slew rate is set
by the value of the feedback resistors and the internal
capacitance. Larger feedback resistors will reduce the
slew rate as will lower supply voltages, similar to the way
the bandwidth is reduced. The photos (Figures 5a, 5b and
5c) show the large-signal response of the LT1207 or
various gain configurations. The slew rate varies from
860V/µs for a gain of 1, to 1400V/µs for a gain of –1.
When the LT1207 is used to drive capacitive loads, the
available output current can limit the overall slew rate. In
the fastest configuration, the LT1207 is capable of a slew
rate of over 1V/ns. The current required to slew a capacitor
Figure 5b. Large-Signal Response, AV = –1
LT1207 • F05b
R
F
= RG = 750Ω
R
L
= 50ΩV
S
= ±15V
The amplifier’s supply current will be approximately 40
times the current in the Shutdown pin. The voltage across
the resistor in this condition is V
+
– 3V
BE
. For example, a
60k resistor will set the amplifier’s supply current to 10mA
with V
S
= ±15V.
The photos (Figures 4a and 4b) show the effect of reducing
the quiescent supply current on the large-signal response.
The quiescent current can be reduced to 5mA in the
inverting configuration without much change in response.
In noninverting mode, however, the slew rate is reduced
as the quiescent current is reduced.
Figure 4a. Large-Signal Response vs IQ, AV = –1
Figure 4b. Large-Signal Response vs IQ, AV = 2
LT1207 • F04a
R
F
= 750Ω
R
L
= 50ΩI
Q
= 5mA, 10mA, 20mA
V
S
= ±15V
LT1207 • F04b
R
F
= 750Ω
R
L
= 50ΩI
Q
= 5mA, 10mA, 20mA
V
S
= ±15V
Slew Rate
Unlike a traditional op amp, the slew rate of a current
feedback amplifier is not independent of the amplifier gain
configuration. There are slew rate limitations in both the
input stage and the output stage. In the inverting mode,
LT1207 • F05a
R
F
= 825Ω
R
L
= 50ΩV
S
= ±15V
Figure 5a. Large-Signal Response, AV = 1
11
LT1207
Figure 5c. Large-Signal Response, AV = 2
Capacitance on the Inverting Input
Current feedback amplifiers require resistive feedback
from the output to the inverting input for stable operation.
Take care to minimize the stray capacitance between the
output and the inverting input. Capacitance on the invert-
ing input to ground will cause peaking in the frequency
response (and overshoot in the transient response), but it
does not degrade the stability of the amplifier.
Power Supplies
The LT1207 will operate from single or split supplies from
±5V (10V total) to ±15V (30V total). It is not necessary to
use equal value split supplies, however the offset voltage
and inverting input bias current will change. The offset
voltage changes about 500µV per volt of supply mis-
match. The inverting bias current can change as much as
5µA per volt of supply mismatch, though typically the
change is less than 0.5µA per volt.
Thermal Considerations
Each amplifier in the LT1207 includes a separate thermal
shutdown circuit which protects against excessive inter-
nal (junction) temperature. If the junction temperature
exceeds the protection threshold, the amplifier will begin
cycling between normal operation and an off state. The
cycling is not harmful to the part. The thermal cycling
occurs at a slow rate, typically 10ms to several seconds,
which depends on the power dissipation and the thermal
time constants of the package and heat sinking. Raising
the ambient temperature until the device begins thermal
shutdown gives a good indication of how much margin
there is in the thermal design.
Heat flows away from the amplifier through the package’s
copper lead frame. Heat sinking is accomplished by using
the heat spreading capabilities of the PC board and its
copper traces. Experiments have shown that the heat
spreading copper layer does not need to be electrically
connected to the tab of the device. The PCB material can
be very effective at transmitting heat between the pad area
attached to the tab of the device and a ground or power
plane layer either inside or on the opposite side of the
board. Although the actual thermal resistance of the PCB
material is high, the length/area ratio of the thermal
U
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LT1207 • F05c
R
F
= 750Ω
R
L
= 50Ω
Differential Input Signal Swing
The differential input swing is limited to about ±6V by an
ESD protection device connected between the inputs. In
normal operation, the differential voltage between the
input pins is small, so this clamp has no effect; however,
in the shutdown mode the differential swing can be the
same as the input swing. The clamp voltage will then set
the maximum allowable input voltage. To allow for some
margin, it is recommended that the input signal be less
than ±5V when the device is shut down.
LT1207 • F06
Figure 6. Large-Signal Response, CL = 10,000pF
V
S
= ±15V
R
F
= RG = 3k R
L
= ∞
at this rate is 1mA per picofarad of capacitance, so
10,000pF would require 10A! The photo (Figure 6) shows
the large-signal behavior with C
L
= 10,000pF. The slew
rate is about 60V/µs, determined by the current limit of
600mA.
12
LT1207
resistance between the layer is small. Copper board stiff-
eners and plated through holes can also be used to spread
the heat generated by the device.
Table 1 lists thermal resistance for several different board
sizes and copper areas. All measurements were taken in
still air on 3/32" FR-4 board with 2oz copper. This data can
be used as a rough guideline in estimating thermal resis-
tance. The thermal resistance for each application will be
affected by thermal interactions with other components as
well as board size and shape.
Table 1. Fused 16-Lead SO Package
TOTAL THERMAL RESISTANCE
TOPSIDE BACKSIDE COPPER AREA (JUNCTION-TO-AMBIENT)
2500 sq. mm 2500 sq. mm 5000 sq. mm 40°C/W
1000 sq. mm 2500 sq. mm 3500 sq. mm 46°C/W
600 sq. mm 2500 sq. mm 3100 sq. mm 48°C/W
180 sq. mm 2500 sq. mm 2680 sq. mm 49°C/W
180 sq. mm 1000 sq. mm 1180 sq. mm 56°C/W
180 sq. mm 600 sq. mm 780 sq. mm 58°C/W
180 sq. mm 300 sq. mm 480 sq. mm 59°C/W
180 sq. mm 100 sq. mm 280 sq. mm 60°C/W
180 sq. mm 0 sq. mm 180 sq. mm 61°C/W
where:
T
J
= Junction Temperature
T
A
= Ambient Temperature
P
D
= Device Dissipation
θ
JA
= Thermal Resistance (Junction-to-Ambient)
As an example, calculate the junction temperature for the
circuit in Figure 8 assuming a 70°C ambient temperature.
The device dissipation can be found by measuring the
supply currents, calculating the total dissipation and then
subtracting the dissipation in the load and feedback
network.
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The dissipation for each amplifier is:
P
D
= (37.5mA)(30V) – (12V)
2
/(1k||1k) = 0.837W
The total dissipation is P
D
= 1.674W. When a 2500 sq mm
PC board with 2oz copper on top and bottom is used, the
thermal resistance is 40°C/W. The junction temperature T
J
is:
T
J
= (1.674W)(40°C/W) + 70°C = 137°C
The maximum junction temperature for the LT1207 is
150°C, so the heat sinking capability of the board is
adequate for the application.
If the copper area on the PC board is reduced to 280mm
2
the thermal resistance increases to 60°C/W and the junc-
tion temperature becomes:
T
J
= (1.674W)(60°C/W) + 70°C = 170°C
Which is above the maximum junction temperature indi-
cating that the heat sinking capability of the board is
inadequate and should be increased.
COPPER AREA (2oz)
COPPER AREA (mm
2
)
0
THERMAL RESISTANCE (°C/W)
70
60
50
40
30
20
10
0
LT1207 • F07
2000 5000
1000 3000 4000
Figure 7. Thermal Resistance vs Total Copper Area
(Top + Bottom)
Calculating Junction Temperature
The junction temperature can be calculated from the
equation:
T
J
= (P
D
)(θ
JA
) + T
A
–
+
15V
–15V
0.01µF
1k
330Ω
1k 200pF
–12V
12V
f = 2MHz
37.5mA
I
LT1206 • F07
1/2 LT1207
SHDN
Figure 8. Thermal Calculation Example
13
LT1207
TYPICAL APPLICATIO S
U
–
+
LT1097
–
+
1/2 LT1207
V
IN
SHDN
COMP
0.01µF
3k330Ω
10k
1k
OUT
OUTPUT OFFSET: < 500µV
SLEW RATE: 2V/µs
BANDWIDTH: 4MHz
STABLE WITH C
L
< 10nF
LT1207 • TA02
500pF
–
+
LT1115
1µF
15V
1µF
–15V
68pF
1µF
15V
1µF
–
+
1/2 LT1207
0.01µF
–15V 560Ω560Ω
909Ω
100Ω
R
L
OUTPUT
R
L
= 32Ω
V
O
= 5V
RMS
THD + NOISE = 0.0009% AT 1kHz
= 0.004% AT 20kHz
SMALL-SIGNAL 0.1dB BANDWIDTH = 600kHz
LT1207 • TA03
SHDN
++
+
+
Gain of Eleven High Current Amplifier
Gain of Ten Buffered Line Driver
14
LT1207
TYPICAL APPLICATIO S
U
–
+
1/2 LT1207
SHDN
–15V
15V
24k
10k
5V
2N3904
LT1207 • TA04
CMOS Logic to Shutdown Interface
–
+
1/2 LT1207
SHDN
75Ω
V
IN
R
F
R
G
75Ω
75Ω
75Ω
75Ω
75Ω CABLE
LT1207 • TA05
Distribution Amplifier
Differential Input—Differential Output Power Amplifier (AV = 4)
Buffer AV = 1
–
+
1/2 LT1207
SHDN 0.01µF*
V
OUT
R
F
**
V
IN
LT1207 • TA06
OPTIONAL, USE WITH CAPACITIVE LOADS
VALUE OF R
F
DEPENDS ON SUPPLY
VOLTAGE AND LOADING. SELECT
FROM TYPICAL AC PERFORMANCE
TABLE OR DETERMINE EMPIRICALLY
*
**
COMP
Differential Output Driver
–
+
+
–
1k
1k
1k
0.01µF
0.01µF
500Ω
+
–
V
IN
V
OUT
LT1207 • TA07
1/2 LT1207
1/2 LT1207
–
+
+
–
1k
1k
1k
+
–
+
–
VOUT
VIN
LT1207 • TA08
1/2 LT1207
1/2 LT1207
15
LT1207
TYPICAL APPLICATIO S
U
–
+
–
+
1k
1k
3Ω
3Ω
1k
1k
V
IN
V
OUT
LT1207 • TA09
1/2 LT1207
1/2 LT1207
Paralleling Both CFAs for Guaranteed 500mA Output Drive Current
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
0.016 – 0.050
0.406 – 1.270
0.010 – 0.020
(0.254 – 0.508)× 45°
0° – 8° TYP
0.008 – 0.010
(0.203 – 0.254)
12345678
0.150 – 0.157**
(3.810 – 3.988)
16 15 14 13
0.386 – 0.394*
(9.804 – 10.008)
0.228 – 0.244
(5.791 – 6.197)
12 11 10 9
S16 0695
0.053 – 0.069
(1.346 – 1.752)
0.014 – 0.019
(0.355 – 0.483)
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
TYP
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
S Package
16-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of circuits as described herein will not infringe on existing patent rights.
16
LT1207
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX
: (408) 434-0507
●
TELEX
: 499-3977
LINEAR TECHN O LO G Y CORP O RATIO N 1996
LT/GP 0196 10K • PRINTED IN USA
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
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Gain, 0.17° Differential Phase, with A
V
= 2 and R
L
= 30Ω, Stable with
C
L
= 10,000pF, Shutdown Control Reduces Supply Current to 200µA
LT1210 Single 1A/30MHz Current Feedback Amplifier Higher Output Current Version of LT1206
LT1229/LT1230 Dual/Quad 100MHz Current Feedback Amplifiers Low Cost CFA for Video Applications, 1000V/µs Slew Rate, 30mA
Output Drive Current, 0.04% Differential Gain, 0.1° Differential
Phase, with A
V
= 2 and R
L
= 150Ω, 9.5mA Max Supply Current per
Op Amp, ±2V to ±15V Supply Range
LT1360/LT1361/LT1362 Single/Dual/Quad 50MHz, 800V/µs, Fast Settling Voltage Feedback Amplifier, 60ns Settling Time to 0.1%,
C-LoadTM Op Amps 10V Step, 5mA Max Supply Current per Op Amp, 9nV√Hz Input Noise
Voltage, Drives All Capacitive Loads, 1mV Max V
OS
, 0.2% Differential
Gain, 0.3° Differential Phase with A
V
= 2 and R
L
= 150Ω
C-Load is a trademark of Linear Technology Corporation
CCD Clock Driver. Two 3rd Order Gaussian Filters Produce Clean CCD Clock Signals
CLK
D
Q
Q
CLOCK
INPUT
1k
100pF
1k 1k
91pF
–
+
1k 0.01µF
510Ω
20V
45pF
1k
100pF
1k 1k
91pF
–
+
1k
0.01µF
510Ω
–10V
45pF
10Ω
10Ω
3300pF
3300pF
CCD ARRAY LOAD
LT1207 • TA10
5
0
CLOCK
INPUT
15
0
DRIVER
OUTPUT
74HC74 1/2 LT1207
1/2 LT1207
TYPICAL APPLICATION
U
