Datasheet

AD829 Data Sheet
Rev. I | Page 16 of 20
HIGH GAIN VIDEO BANDWIDTH, 3-OP-AMP
INSTRUMENTATION AMPLIFIER
Figure 48 shows a 3-op-amp instrumentation amplifier circuit
that provides a gain of 100 at video bandwidths. At a circuit gain of
100, the small signal bandwidth equals 18 MHz into a FET probe.
Small signal bandwidth equals 6.6 MHz with a 50 Ω load. The
0.1% settling time is 300 ns.
The input amplifiers operate at a gain of 20, while the output
op amp runs at a gain of 5. In this circuit, the main bandwidth
limitation is the gain/bandwidth product of the output amplifier.
Extra care should be taken while breadboarding this circuit
because even a couple of extra picofarads of stray capacitance at the
compensation pins of A1 and A2 will degrade circuit bandwidth.
Figure 48. High Gain Video Bandwidth, 3-Op-Amp In-Amp Circuit
00880-048
+15V
–15V
COMM
10µF
10µF
0.1µF
0.1µF
1µF
1µF
0.1µ
F
0.1µF
+V
S
–V
S
PIN 4
EACH
AM
PLIFIER
PIN 7
100Hz
1MHz
10MHz
64.6dB
44.7dB
23.9dB
INPUT
FREQUENCY CMRR
A1
AD829
2pF TO 8pF
SETTLING TIME
AC CMR ADJUST
3pF
3pF
1pF
1pF
2kΩ
200Ω
R
G
210Ω
1kΩ
2kΩ
200Ω
970Ω
50Ω
2kΩ
(G = 5)
5
3
2
6
DC CMR
ADJUST
3pF
(G = 20)
(G = 20)
A2
AD829
A3
AD848
+V
IN
+V
IN
CIRCUIT GAIN = + 1
4000Ω
R
G
5
5
2
3
6
5
3
2
6
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