5962-89807012A 데이터 시트보기 (PDF) - Analog Devices
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5962-89807012A Datasheet PDF : 12 Pages
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AD630
the system input tied to 0 V, and a switching or carrier wave-
form applied to the comparator, a low level square wave will
appear at the output. The differential offset adjustment potenti-
ometers can be used to null the amplitude of this square wave
(Pins 3 and 4). The common-mode offset adjustment can be
used to zero the residual dc output voltage (Pins 5 and 6).
These functions should be implemented using 10k trim poten-
tiometers with wipers connected directly to Pin 8 as shown in
Figures 9a and 9b.
CHANNEL STATUS OUTPUT
The channel status output, Pin 7, is an open collector output
referenced to –VS that can be used to indicate which of the two
input channels is active. The output will be active (pulled low)
when Channel A is selected. This output can also be used to
supply positive feedback around the comparator. This produces
hysteresis which serves to increase noise immunity. Figure 7
shows an example of how hysteresis may be implemented. Note
that the feedback signal is applied to the inverting (–) terminal
of the comparator to achieve positive feedback. This is because
the open collector channel status output inverts the output sense
of the internal comparator.
1M⍀
+5V
100k⍀
9
10
100⍀
100k⍀
7
8
–15V
Figure 7. Comparator Hysteresis
The channel status output may be interfaced with TTL inputs
as shown in Figure 8. This circuit provides appropriate level
shifting from the open-collector AD630 channel status output to
TTL inputs.
+5V
AD630
+15V
100k⍀
6.8k⍀
7
2N2222
22k⍀
IN 914s
TTL INPUT
AD630 when used to modulate a 100 kHz square wave carrier
with a 10 kHz sinusoid. The result is the double sideband sup-
pressed carrier waveform.
These balanced modulator topologies accept two inputs, a signal
(or modulation) input applied to the amplifying channels and a
reference (or carrier) input applied to the comparator.
MODULATION
INPUT
CARRIER
INPUT
10k⍀ CM
ADJ
10k⍀ DIFF
ADJ
6
5
2.5k⍀
1
AMP A
2
A
20
2.5k⍀
B
17
AMP B
18
19
COMP
9
10
4
3
12
11
13
10k⍀
–V
14
10k⍀
15
AD630
16
5k⍀
7
8
+VS
MODULATED
OUTPUT
SIGNAL
–VS
Figure 9a. AD630 Configured as a Gain-of-One Balanced
Modulator
MODULATION
INPUT
CARRIER
INPUT
10k⍀ CM
ADJ
10k⍀ DIFF
ADJ
6
5
2.5k⍀
1
AMP A
2
A
20
2.5k⍀
B
17
AMP B
18
19
COMP
9
10
4
3
12
11
13
10k⍀
–V
14
10k⍀
15
AD630
16
5k⍀
7
8
+VS
MODULATED
OUTPUT
SIGNAL
–VS
Figure 9b. AD630 Configured as a Gain-of-Two Balanced
Modulator
8
–15V
Figure 8. Channel Status—TTL Interface
APPLICATIONS: BALANCED MODULATOR
Perhaps the most commonly used configuration of the AD630 is
the balanced modulator. The application resistors provide precise
symmetric gains of ± 1 and ± 2. The ± 1 arrangement is shown in
Figure 9a and the ± 2 arrangement is shown in Figure 9b. These
cases differ only in the connection of the 10 kΩ feedback resistor
(Pin 14) and the compensation capacitor (Pin 12). Note the use
of the 2.5 kΩ bias current compensation resistors in these
examples. These resistors perform the identical function in the
± 1 gain case. Figure 10 demonstrates the performance of the
5V
5V
20s
MODULATION
INPUT
CARRIER
INPUT
10V
OUTPUT
SIGNAL
Figure 10. Gain-of-Two Balanced Modulator Sample
Waveforms
–8–
REV. E
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