a

AD630

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REV. E

Balanced Modulator/Demodulator

FUNCTIONAL BLOCK DIAGRAM

CM OFF

ADJ

CM OFF

ADJ

DIFF OFF

ADJ

DIFF OFF

ADJ

6

3

4

5

2.5k

AMP A

2.5k

AMP B

–V

10k

10k

17

5k

8

9

10

COMP

19

18

1

15

7

16

14

13

11

12

CH A+

CH A–

CH B+

CH B–

SEL B

SEL A

2

20

COMP

CHANNEL

STATUS

B/A

AD630

A

B

PRODUCT DESCRIPTION

The AD630 is a high precision balanced modulator that combines

a flexible commutating architecture with the accuracy and tem-

perature stability afforded by laser wafer trimmed thin film

resistors. Its signal processing applications include balanced

modulation and demodulation, synchronous detection, phase

detection, quadrature detection, phase-sensitive detection,

lock-in amplification, and square wave multiplication. A network

of on-board applications resistors provides precision closed-loop

gains of

±1 and ±2 with 0.05% accuracy (AD630B). These

resistors may also be used to accurately configure multiplexer

gains of +1, +2, +3, or +4. Alternatively, external feedback may

be employed, allowing the designer to implement high gain or

complex switched feedback topologies.

The AD630 can be thought of as a precision op amp with two

independent differential input stages and a precision comparator

that is used to select the active front end. The rapid response

time of this comparator coupled with the high slew rate and fast

settling of the linear amplifiers minimize switching distortion. In

addition, the AD630 has extremely low crosstalk between chan-

nels of –100 dB @ 10 kHz.

The AD630 is used in precision signal processing and instru-

mentation applications that require wide dynamic range. When

used as a synchronous demodulator in a lock-in amplifier

configuration, it can recover a small signal from 100 dB of inter-

fering noise (see Lock-In Amplifier Applications section). Although

optimized for operation up to 1 kHz, the circuit is useful at

frequencies up to several hundred kilohertz.

Other features of the AD630 include pin programmable frequency

compensation, optional input bias current compensation resis-

tors, common-mode and differential-offset voltage adjustment,

and a channel status output that indicates which of the two

differential inputs is active. This device is now available to

Standard Military Drawing (DESC) numbers 5962-8980701RA

and 5962-89807012A.

PRODUCT HIGHLIGHTS

1. The configuration of the AD630 makes it ideal for signal

processing applications, such as balanced modulation and

demodulation, lock-in amplification, phase detection, and

square wave multiplication.

2. The application flexibility of the AD630 makes it the best

choice for applications that require precisely fixed gain,

switched gain, multiplexing, integrating-switching functions,

and high speed precision amplification.

3. The 100 dB dynamic range of the AD630 exceeds that of any

hybrid or IC balanced modulator/demodulator and is compa-

rable to that of costly signal processing instruments.

4. The op amp format of the AD630 ensures easy implementa-

tion of high gain or complex switched feedback functions.

The application resistors facilitate the implementation of

most common applications with no additional parts.

5. The AD630 can be used as a 2-channel multiplexer with

gains of +1, +2, +3, or +4. The channel separation of

100 dB @ 10 kHz approaches the limit achievable with an

empty IC package.

6. The AD630 has pin strappable frequency compensation (no

external capacitor required) for stable operation at unity gain

without sacrificing dynamic performance at higher gains.

7. Laser trimming of comparator and amplifying channel offsets

eliminates the need for external nulling in most cases.

FEATURES

Recovers Signal from 100 dB Noise

2 MHz Channel Bandwidth

45 V/ s Slew Rate

–120 dB Crosstalk @ 1 kHz

Pin Programmable, Closed-Loop Gains of

1 and

2

0.05% Closed-Loop Gain Accuracy and Match

100

V Channel Offset Voltage (AD630BD)

350 kHz Full Power Bandwidth

Chips Available