AD633_15 Datasheet, PDF (11/21 Pages) Analog Devices – Low Cost Analog Multiplier

AD633
Data Sheet
Likewise, Figure 16 shows how to implement a divider using a
multiplier in a feedback loop. The transfer function for the
divider is
W′ = − (10 V ) ^E
(6)
E_X
R
10kΩ
R
10kΩ
E
+15V
0.1µF
E_X
7
2
AD711 ⁶
3
4
0.1µF
1 X1
+15V
+V_S 8
0.1µF
2 X2
W7
AD633JN
3 Y1
Z6
4 Y2
–V_S 5
0.1µF
–15V
–15V
E
W' = –10V _EX
Figure 16. Connections for Division
VARIABLE SCALE FACTOR
In some instances, it may be desirable to use a scaling voltage
other than 10 V. The connections shown in Figure 17 increase
the gain of the system by the ratio (R1 + R2)/R1. This ratio is
limited to 100 in practical applications. The summing input, S,
can be used to add an additional signal to the output, or it can
be grounded.
+15V
+
X
INPUT _–
+
Y
INPUT _–
1 X1
+V_S 8
2 X2
W7
AD633JN
3 Y1
Z6
0.1µF
W = ^{(X1 – X2)(Y1 – Y2) R1 + R2} + S
R1
10V
R1
1kΩ ≤ R1, R2 ≤ 100kΩ
4 Y2
–V_S 5
0.1µF
R2
S
–15V
Figure 17. Connections for Variable Scale Factor
CURRENT OUTPUT
The voltage output of the AD633 can be converted to a current
output by the addition of a resistor, R, between the W and Z pins of
the AD633 as shown in Figure 18.
+15V
X
+
INPUT _–
+
Y
INPUT _–
1 X1
+V_S 8
2 X2
W7
AD633JN
3 Y1
Z6
0.1µF
R
4 Y2
–V_S 5
0.1µF
1 (X1 – X2)(Y1 – Y2)
I_O = _R
10V
1kΩ ≤ R ≤ 100kΩ
–15V
Figure 18. Current Output Connections
This arrangement forms the basis of voltage-controlled integrators
and oscillators as is shown later in this section. The transfer
function of this circuit has the form
I_O
=
1
R
(X1
−
X2)(Y1 −
10 V
Y2)
(7)
LINEAR AMPLITUDE MODULATOR
The AD633 can be used as a linear amplitude modulator with no
external components. Figure 19 shows the circuit. The carrier
and modulation inputs to the AD633 are multiplied to produce
a double sideband signal. The carrier signal is fed forward to the
Z input of the AD633 where it is summed with the double
sideband signal to produce a double sideband with the carrier
output.
+15V
MODULATION +
INPUT
±E_{M –}
CARRIER
INPUT
E_C sin ωt
1 X1
+V_S 8
2 X2
W7
AD633JN
3 Y1
Z6
4 Y2
–V_S 5
0.1µF
W = 1+ ^EM
10V
E_C sin ωt
0.1µF
–15V
Figure 19. Linear Amplitude Modulator
VOLTAGE-CONTROLLED, LOW-PASS AND HIGH-
PASS FILTERS
Figure 20 shows a single multiplier used to build a voltage-
controlled, low-pass filter. The voltage at Output A is a result
of filtering ES. The break frequency is modulated by EC, the control
input. The break frequency, f2, equals
f₂ =
E_C
(8)
10 ( 2π RC )
and the roll-off is 6 dB per octave. This output, which is at a
high impedance point, may need to be buffered.
CONTROL
INPUT E_C
SIGNAL
INPUT E_S
dB
f₂ f₁
0
f
+15V
1 X1
+V_S 8
–6dB/OCTAVE
0.1µF
OUTPUT A
OUTPUT B
2 X2
W7
AD633JN
3 Y1
Z6
4 Y2
–V_S 5
0.1µF
OUTPUT B = ^{1 + T1P}
1 + T₂P
R
1
OUTPUT A =
1 + T₂P
C
1
T₁ = _{ω 1} = RC
–15V
1 10RC
T₂ = _{ω 2} = _EC
Figure 20. Voltage-Controlled, Low-Pass Filter
The voltage at Output B, the direct output of the AD633, has the
same response up to frequency f1, the natural breakpoint of RC
filter, and then levels off to a constant attenuation of f1/f2 = 10/EC
f₁
=
2
1
π RC
(9)
Rev. J | Page 10 of 20