ad829sq-883b Analog Devices, Inc., ad829sq-883b Datasheet - Page 13

• Manufacturer Part Number: ad829sq-883b
• Description: High-speed, Low-noise Video Op Amp
• Manufacturer: Analog Devices, Inc.

Figure 16. Closed-Loop Frequency Response vs. Supply
for the Inverting Amplifier Using Current Feedback
Compensation
A Low Error Video Line Driver
The buffer circuit shown in Figure 18 will drive a back-terminated
75 Ω video line to standard video levels (1 V p-p) with 0.1 dB
gain flatness to 30 MHz with only 0.04° and 0.02% differential
phase and gain at the 4.43 MHz PAL color subcarrier frequency.
This level of performance, which meets the requirements for high
definition video displays and test equipment, is achieved using
only 5 mA quiescent current.
A High Gain, Video Bandwidth, Three Op Amp In Amp
Figure 19 shows a three 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.
REV. G
+V
+V
210
IN
IN
R
G
–17
–20
–23
–26
–29
–32
–35
–38
–41
–44
–47
1
A1
A2
2k
1pF
1pF
2k
V
R
R
GAIN = –1
C
3pF
3pF
IN
L
F
COMP
AD829
= 1k
= 1k
(G = 20)
(G = 20)
AD829
= –20dBM
= 4pF
Figure 19. A High Gain, Video Bandwidth, Three Op Amp In Amp Circuit
FREQUENCY (MHz)
10
200
200
3pF
CIRCUIT GAIN =
50
970
DC CMR
ADJUST
AC CMR ADJUST
SETTLING TIME
15V
2pF to 8pF
5V
A3
1k
(
4000
AD848
100
(G = 5)
R
G
+ 1
(
5
–13–
2k
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, since
even a couple of extra picofarads of stray capacitance at the com-
pensation pins of A1 and A2 will degrade circuit bandwidth.
Figure 17. Noninverting Amplifier Connection Using
Current Feedback Compensation
Figure 18. A Video Line Driver with a Flatness over
Frequency Adjustment
COMM
–15V
V
+15V
V
IN
IN
CABLE
COAX
50
10 F
10 F
75
0.1 F
0.1 F
50
FREQUENCY
C
100 Hz
1 MHz
10 MHz
0.1 F
0.1 F
30pF
INPUT
–15V
COMP
0.1 F
AD829
+15V
AD829
+15V
+V
–V
–15V
64.6dB
44.7dB
23.9dB
S
S
CMRR
3pF
C
COMP
0.1 F
1 F
1 F
300
300
75
2k
2k
50
0.1 F
0.1 F
CABLE
CABLE
COAX
COAX
75
50
OPTIONAL
2pF to 7pF
FLATNESS
TRIM
PIN 7
PIN 4
AD829
EACH
AMPLIFIER
75
50
V
V
OUT
OUT