MC1494P ONSEMI [ON Semiconductor], MC1494P Datasheet - Page 13

• Manufacturer Part Number: MC1494P
• Description: LINEAR FOUR-QUADRANT MULTIPLIER INTEGRATED CIRCUIT
• Manufacturer: ONSEMI [ON Semiconductor]

The adjustment procedure for this circuit is quite simple.
1.
2.
offsets will be a function of the type of potentiometers used
for P1 and P2. Multiple turn cermet type potentiometers
are recommended.
Frequency Doubler
then the output is given by,
which reduces to,
term equal to one half the peak voltage squared and the
second harmonic of the input frequency. Thus, the circuit acts
as a frequency doubler. Two facts about this circuit are
worthy of note. First, the second harmonic of the input
frequency is the only frequency appearing at the output. The
fundamental does not appear. Second, if the input is
e c = 1 V pk
e m = 2 V pk
e m
MOTOROLA ANALOG IC DEVICE DATA
e c
Again, the ability to make careful adjustment of these
This equation states that the output will consist of a DC
If for Figure 27 both inputs are identical:
Place the carrier signal at Pin 10. With no signal applied
to Pin 9, adjust potentiometer P1 such that an AC null is
obtained at the output.
Place a modulation signal at Pin 9. With no signal
applied to Pin 10, adjust potentiometer P2 such that an
AC null is obtained at the output.
R
R
10
9
16 k
11
+
+
1
Figure 27. Balanced Modulator
3.0 k
12
3
e o =
e o = e m e c = E 2 cos 2 t
e m = e c = E cos t
6
E 2
7
MC1494
2
6.2 k
(1 + cos2 t)
13
0.1 F
8
4
–15 V +15 V
51 k
20 k
20 k
15
P2
P1
5
2
14
R L
0.1 F
e o = e m e c
e o = Ke c e m
4.7 k
K = 1
MC1494
sinusoidal, the output will be sinusoidal and requires no
filtering.
doubler with input frequencies in excess of 2.0 MHz.
Amplitude Modulator
modulator. This is accomplished by simply varying the input
offset adjust potentiometer (P1) associated with the
mudulation input. This procedure places a DC offset on the
modulation input of the multiplier such that the carrier still
passes through the multiplier when the modulating signal is
zero. The result is amplitude modulation. This is easily seen
by examining the basic mathematical expression for
amplitude modulation given below. For the case under
discussion, with K = 1,
where E is the DC input offset adjust voltage. This expression
can be written as:
where, E o = EE c
From this, it is easy to see that 100% modulation can be
achieved by adjusting the input offset adjust voltage to be
exactly equal to the peak value of the modulation (E m ). This
is done by observing the output waveform and adjusting the
input offset potentiometer (P1) until the output exhibits the
familiar amplitude modulation waveform.
Phase Detector
identical frequency, but having a relative phase shift, the
output will be a DC signal which is directly proportional to the
cosine of phase difference as well as the double frequency
term.
eliminates the second cosine term) and return of R L to an
offset adjustment potentiometer will result in a DC output
voltage which is proportional to the cosine of the phase
difference. Hence, the circuit functions as a synchronous
detector.
The circuit of Figure 27 can be used as a frequency
The circuit of Figure 27 is also easily used as an amplitude
This is the standard equation for amplitude modulation.
If the circuit of Figure 27 has as its inputs two signals of
The addition of a simple low pass filter to the output (which
and, M =
or, e o =
e o = (E + E m cos m t) (E c cos c t)
e o = E o [1 + M cos c t] cos c t
e c = E c cos c t
e m = E m cos( c t + )
e o = e c e m = E c E m cos c t cos( c t + )
E m
E c E m
E
2
= modulation index.
[cos + cos(2 c t + )]
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