Data Sheet AD829
Rev. I | Page 15 of 20
Figure 44 and Figure 45 show the closed-loop frequency
response of the AD829 for different closed-loop gains and
different supply voltages.
Figure 44. Closed-Loop Frequency Response for the Inverting Amplifier Using
Current Feedback Compensation
Figure 45. Closed-Loop Frequency Response vs. Supply for the Inverting
Amplifier Using Current Feedback Compensation
When a noninverting amplifier configuration using a current
feedback compensation is needed, the circuit shown in Figure 46 is
recommended. This circuit provides a slew rate twice that of the
shunt compensated noninverting amplifier of Figure 47 at the
expense of gain flatness. Nonetheless, this circuit delivers 95 MHz
bandwidth with 1 dB flatness into a back-t
erminated cable,
wit
h a differential gain error of only 0.01% and a differential
phase error of only 0.015 at 4.43 MHz.
Figure 46. Noninverting Amplifier Connection Using Current Feedback
Compensation
Figure 47. Video Line Driver with a Flatness over Frequency Adjustment
LOW ERROR VIDEO LINE DRIVER
The buffer circuit shown in Figure 47 drives a back-terminated
75 Ω video line to standard video levels (1 V p-p), with 0.1 dB
gain flatness to 30 MHz and 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.
00880-044
FREQUENCY (MHz)
CLOSED-LOOP GAIN (dB)
1 10
–15
–12
–9
–6
–3
0
3
6
9
12
15
100
GAIN = –4
C
COMP
= 2pF
GAIN = –2
C
COMP
= 3pF
GAIN = –1
C
COMP
= 4pF
V
S
= ±15V
R
L
= 1kΩ
R
F
= 1kΩ
V
IN
= –30dBm
00880-045
FREQUENCY (MHz)
OUTPUT LEVEL (dB)
1 10
–47
–44
–41
–38
–35
–32
–29
–26
–23
–20
–17
100
±5V
±15V
V
IN
= –20dBm
R
L
= 1kΩ
R
F
= 1kΩ
GAIN = –1
C
COMP
= 4pF
00880-046
3
2
7
6
4
5
+
–
AD829
+15V
–15V
0.1µF
3pF
C
COMP
2kΩ
2kΩ
0.1µF
50Ω
50kΩ
50Ω
50Ω
COAX
CABLE
50Ω
COAX
CABLE
V
IN
V
OUT
00880-047
3
2
7
6
5
4
+
–
AD829
+15V
0.1µF
30pF
C
COMP
–15V
0.1µF
300Ω
300Ω
75Ω
75Ω
75Ω
50Ω
COAX
CABLE
V
IN
V
OUT
OPTIONAL
2pF TO 7pF
FLATNESS
TRIM
