AD830A(RevA) 查看數據表（PDF） - Analog Devices

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AD830A
(Rev.:RevA)

High Speed, Video Difference Amplifier

Analog Devices 

AD830

AC COUPLED LINE RECEIVER

The AD830 is configurable as an ac coupled differential ampli-

fier on a single or bipolar supply voltages. All that is needed is

inclusion of a few noncritical passive components as illustrated

below in Figure 42. A simple resistive network at the X GM

input establishes a common-mode bias. Here, the common

mode is centered at 6 volts, but in principle can be any voltage

within the common-mode limits of the AD830. The 10 kΩ re-

sistors to each input bias the X GM stage with sufficiently high

impedance to keep the input coupling corner frequency low, but

not too large so that residual bias current induced offset voltage

becomes troublesome. For dual supply operation, the 10 kΩ

resistors may go directly to ground. The output common is con-

veniently set by a Zener diode for a low impedance reference to

preserve the high frequency CMR. However, a simple resistive

divider will work fine and good high frequency CMR can be

maintained by placing a compensating resistor in series with the

+Y input. The excellent CMRR response of the circuit is shown

in Figure 43. A plot of the 0.1 dB flatness from 10 Hz is also

shown. With the use of 10 µF capacitors, the CMR is >90 dB

down to a few tens of hertz. This level of performance is almost

impossible to achieve with discrete solutions.

INPUT

SIGNAL

10µF

ZCM

RT

10µF

10kΩ 10kΩ

+VS

2kΩ*

10kΩ

1

GM

2

3

GM

4

10kΩ

*OPTIONAL TUNING FOR

IMPROVING VERY LOW

FREQUENCY CMR.

AD830

A=1

C

+12V

0.1µF

8

75Ω

COAX

VOUT 75Ω CABLE

7

1000µF

6

75Ω

5

+12V

4.7kΩ

1N4736

6.8V

Figure 42. AC Coupled Line Receiver

120

WITH CIRCUIT TRIMMED

USING EXTERNAL 2kΩ

POTENTIOMETER

100

80

WITHOUT EXTERNAL

2kΩ POTENTIOMETER

60

40

20

10

100

1k

10k 100k

1M

10M 100M

FREQUENCY – Hz

Figure 43. Common-Mode Rejection vs. Frequency for

Line Receiver

1

0

–0.1

–0.2

–0.3

–0.4

–0.5

–0.6

–0.7

–0.8

–0.9

10

100

1k

10k

100k

1M

10M

FREQUENCY – Hz

Figure 44. Amplitude Response vs. Frequency for Line

Receiver

REV. A

–15–

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