AD633 Просмотр технического описания (PDF) - Analog Devices
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AD633 Datasheet PDF : 16 Pages
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AD633
Data Sheet
APPLICATIONS INFORMATION
The AD633 is well suited for such applications as modulation
and demodulation, automatic gain control, power measurement,
voltage-controlled amplifiers, and frequency doublers. These
applications show the pin connections for the AD633JN (8-lead
PDIP), which differs from the AD633JR (8-lead SOIC).
MULTIPLIER CONNECTIONS
Figure 11 shows the basic connections for multiplication. The X
and Y inputs normally have their negative nodes grounded, but
they are fully differential, and in many applications, the grounded
inputs may be reversed (to facilitate interfacing with signals of a
particular polarity while achieving some desired output polarity),
or both may be driven.
+15V
X
+
INPUT –
Y
+
INPUT –
1 X1
+VS 8
2 X2
W7
AD633JN
3 Y1
Z6
4 Y2
–VS 5
0.1µF
W = (X1 – X2)(Y1 – Y2) + Z
10V
OPTIONAL SUMMING
INPUT, Z
0.1µF
–15V
Figure 11. Basic Multiplier Connections
SQUARING AND FREQUENCY DOUBLING
As is shown in Figure 12, squaring of an input signal, E, is
achieved simply by connecting the X and Y inputs in parallel to
produce an output of E2/10 V. The input can have either polarity,
but the output is positive. However, the output polarity can be
reversed by interchanging the X or Y inputs. The Z input can be
used to add a further signal to the output.
+15V
0.1µF
E
1 X1
+VS 8
2 X2
W7
AD633JN
3 Y1
Z6
W = E2
10V
4 Y2
–VS 5
0.1µF
–15V
Figure 12. Connections for Squaring
When the input is a sine wave E sin ωt, this squarer behaves as a
frequency doubler, because
E sin t 2
E2
1 cos 2 t
(2)
10 V
20 V
Equation 2 shows a dc term at the output that varies strongly
with the amplitude of the input, E. This can be avoided using
the connections shown in Figure 13, where an RC network is
used to generate two signals whose product has no dc term. It
uses the identity
cos θ sin θ 1 sin 2 θ
(3)
2
E
R
C
+15V
1 X1
+VS 8
2 X2
W7
AD633JN
3 Y1
Z6
4 Y2
–VS 5
0.1µF
W = E2
R1
10V
1kΩ
R2
3kΩ
0.1µF
–15V
Figure 13. Bounceless Frequency Doubler
At ωo = 1/CR, the X input leads the input signal by 45° (and is
attenuated by √2), and the Y input lags the X input by 45° (and
is also attenuated by √2). Because the X and Y inputs are 90° out of
phase, the response of the circuit is (satisfying Equation 3)
W
1
10 V
E
2
sin
0t
45
E
2
sin
0t
45
E2
40 V
sin
2
0t
(4)
which has no dc component. Resistors R1 and R2 are included
to restore the output amplitude to 10 V for an input amplitude
of 10 V.
The amplitude of the output is only a weak function of frequency;
the output amplitude is 0.5% too low at ω = 0.9 ω0 and ω0 = 1.1 ω0.
GENERATING INVERSE FUNCTIONS
Inverse functions of multiplication, such as division and square
rooting, can be implemented by placing a multiplier in the feedback
loop of an op amp. Figure 14 shows how to implement square
rooting with the transfer function for the condition E < 0.
The 1N4148 diode is required to prevent latchup, which can
occur in such applications if the input were to change polarity,
even momentarily.
W 10EV
+15V
10kΩ
E < 0V
2
7
AD711
0.1µF
6
3
4
0.1µF
(5)
10kΩ
1 X1
+15V
+VS 8
0.1µF
2 X2
W7
AD633JN 1N4148
3 Y1
Z6
–15V
4 Y2
–VS 5
0.1µF
–15V
W = 10V)E
Figure 14. Connections for Square Rooting
Rev. I | Page 8 of 16
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