MC1495 ON Semiconductor, MC1495 Datasheet - Page 15

• Manufacturer Part Number: MC1495
• Description: LINEAR FOUR-QUADRANT MULTIPLIER
• Manufacturer: ON Semiconductor

where
frequency and K is the multiplier gain constant.
translation or an operational amplifier; a higher operating
frequency results.
intelligence from single-sideband received signal. The ssb
signal is of the form:
and if multiplied by the appropriate carrier waveform, cos
ascertained in advance, the designer can insert a low pass
filter and obtain the (AK/2) (cos
also can use an operational amplifier for a combination level
shift-active filter, as an external component. But in potted
multipliers, even if the frequency range can be covered, the
operational amplifier is inside and not accessible, so the user
must accept the level shifting provided, and still add a low
pass filter.
Amplitude Modulation
balanced modulation, when a dc term is added to the
input range is limited to 1.0 V
source of 2.0 mA and an R
takes best advantage of the dynamic range and insures linear
operation in the Y-channel.
c
The defining equation for balanced modulation is
AC coupling at the output eliminates the need for level
A problem common to communications is to extract the
If the frequency of the band-limited carrier signal (
The multiplier performs amplitude modulation, similar to
The signal is applied to the unit’s Y-input. Since the total
t,
e
ssb
KE
e
c
carrier
c
is the carrier frequency,
2
E
m
K(E
=
[ cos (
e
m
ssb
cos
AK
2
= A cos (
[cos (2
c
m
+
Y
t) (E
value of 1.0 k is chosen. This
m
pp
)t + cos (
c
c
c
cos
, a 2.0 V swing, a current
c
+
+
t) term with ease. He/she
m
m
c
m
)t + cos (
) t
t) =
c
is the modulator
–
Figure 30. Amplitude Modulation
m
) t ]
c
) t ].
http://onsemi.com
c
) is
MC1495
15
modulating signal with the Y-offset adjust potentiometer
(see Figure 30).
where m indicates the degrees of modulation. Since m is
adjustable, via potentiometer P
possible. Without extensive tweaking, 96% modulation may
be obtained where
modulator example.
Linear Gain Control
of the two MC1495 inputs a signal that will vary the unit’s
gain. The following example demonstrates the feasibility of
this application. Suppose a 200 kHz sinewave, 1.0 V
peak-to-peak, is the signal to which a gain control will be
added. The dynamic range of the control voltage V
to +1.0 V. These must be ascertained and the proper values
of R
the 200 kHz operating frequency, load resistors of 100
were chosen to broaden the operating bandwidth of the
multiplier, but gain was sacrificed. It may be made up with
an amplifier operating at the appropriate frequency (see
Figure 31).
source selected was 1.0 mA, and the R
was 2.0 k . This also insures linear operation over the
X-input dynamic range. Choosing R
bandwidth operation.
Here, the identity is:
E
To obtain linear gain control, the designer can feed to one
Since the X-input varies between 0 and +1.0 V, the current
m
X
(1 + m cos
KE
and R
m
2
E
Y
c
m
can be selected for optimum performance. For
[ cos(
m
t) E
c
and
c
c
cos
+
m
m
are the same as in the balanced
)t + cos (
c
t = KE
1
, 100% modulation is
L
m
= 100 assures wide
E
c
c
cos
X
–
value chosen
m
) t ]
c
t
+
C
is 0 V