FUNCTIONAL BLOCK DIAGRAM
CM OFF
ADJ
CM OFF
ADJ
DIFF OFF
ADJ
DIFF OFF
ADJ
6
34
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
R
IN
A
CHA+
CHA–
R
IN
B
CHB+
CHB–
SEL B
SEL A
2
20
COMP
+V
S
V
OUT
R
B
R
F
R
A
CHANNEL
STATUS
B/A
–V
S
AD630
A
B
REV. C
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reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
Balanced Modulator/Demodulator
AD630
PRODUCT DESCRIPTION
The AD630 is a high precision balanced modulator which com-
bines a flexible commutating architecture with the accuracy and
temperature 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 his own high
gain or complex switched feedback topologies.
The AD630 may be thought of as a precision op amp with two
independent differential input stages and a precision comparator
which 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 intended for use in precision signal processing
and instrumentation applications requiring 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 application). 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 which indicates which of the two
differential inputs is active. This device is now available to Stan-
dard 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 many applications requiring 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 two channel multiplexer with
gains of +1, +2, +3 or +4. The channel separation of
100 dB @ 10 kHz approaches the limit which is 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 ⴞ1 and ⴞ2
0.05% Closed Loop Gain Accuracy and Match
100 V Channel Offset Voltage (AD630BD)
350 kHz Full Power Bandwidth
Chips Available
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 2000
