rc4200 Fairchild Semiconductor, rc4200 Datasheet - Page 16

• Manufacturer Part Number: rc4200
• Description: Analog Multiplier
• Manufacturer: Fairchild Semiconductor

RC4200
Amplitude Modulator with A.G.C.
In many AC modulator applications, unwanted output
modulation is caused by variations in carrier input ampli-
tude. The versatility of the RC4200 multiplier can be utilizes
to eliminate this undesired fluctuation. The extended range
multiplier circuit (Figure 4) shows an output amplitude
inversely proportional to the reference voltage V
By making V
rier input) such that:
Then the denominator becomes a variable value that auto-
matically provides constant gain, such that the modulating
input (V
factor even though the carrier varies in amplitude.
16
i.e., V
V
V
**Determines sacle factor (K) for X function.
+V = +V
-V = -15V
IN
*Determines sacle factor (K) for X function.
REF
s
s
0
=
100K
X
=
REF
100K
) modulates the carrier (V
V
100K
V
--------------- -
V
H
= +15V
REF
X
REF
V
=
Y
∫
proportional to V
(
83.3K
100K
50K
R
------------ -
R
V
0
1
Y
50K
R
R
d
2
)
8
7
1
2
-V
Multiplier
RC4200A
S
2
3
X
2
0.1 F
Y
Y
6
167K
) with a fixed scale
µ
(where V
Figure 15. RMS to DC Converter V
5
4
45.5 K
100
Y
60K
REF
is the car-
RC5532
30K
250K*
22 F
1/2
.
µ
+V
-V
S
S
10K
13.3K
300K
If V
(i.e., 2A/π) and scaled by a value of π/2 then:
V
and if: V
and: V
Then: V
The resistor scaling is determined by the dynamic range of
the carrier variation and modulating input.
The resistor values are solved, as with the other extended
range circuits, in terms of the input voltages.
Input voltages:
H
=A
H
Modulation voltage (V
Carrier (V
Carrier amplitude fluctuation (∆A):
Dynamic Range (N): A(max.)/A(min.),
A(max.) = V
is made proportional to the average value of Asinωt
Y
0
X
Carrier input (Asinωt)
A(min.) sint ≤ V
100K
60K
= K V
80K
OUT
= Modulating input (V
10K
Y
8
7
1
=√V
2
M
): V
H
-V
RC4200A
Multiplier
sinωt where K =
(max.) and A(min.) = V
IN
+V
S
3
Y
2
REF
X
= Asinωt
0.1 F
Y
6
100K
µ
M
≤ A(max.) sinΩωt
5
4
): 0 ≤ V
15K
100
M
PRODUCT SPECIFICATION
)
M
30K
R
------------ -
R
RC5532
0
1
44.4K**
≤ V
300K
R
R
1/2
200K
d
2
REV. 1.2.1 6/14/01
H
X
(min.)
(max.)
+V
-V
S
S
10K
65-1869
V
OUT