ca3256 Intersil Corporation, ca3256 Datasheet - Page 11

• Manufacturer Part Number: ca3256
• Description: 25mhz, Bimos Analog Video Switch Amplifier
• Manufacturer: Intersil Corporation

Any combination of switch input circuits can be configured
with multiple, parallel, line-drive outputs. The video switch
amplifier circuit of Figure 8 illustrates how the CA3256 may
be configured in pairs to provide an 8-to-1 video switch
amplifier using a 3-bit address to select the input. It is also
possible to use the fifth channel input to tie signals to a
common bus line for distribution from the selected amplifier;
however, distributed capacitance loading will result in
reduced bandwidth. The 4 plus 1 combination of input-signal
switching provides for a wide assortment of video switch
circuit configurations.
While the BiMOS process does provide some compromises
for both the switch and the amplifier, the combined system is
capable of the performance needed in most high-quality,
switching applications. As an integrated system, many of the
problems in PC-board layout are simplified, and there is a
reduction in component count. In its simplest form, with
+12V and -5V supplies, the CA3256 may be DC connected
at the input and output; the LED indicators need not be
connected. Under these conditions, the circuit may be as
simple as the one in Figure 8.
Summary
While each video-switch amplifier is designed for a specific
application and, to that end, is tailored as far as performance
to a given set of specifications, the circuit-designer’s goal is
generally the same in every case: to make the best possible
switch for the lowest cost. In this respect, the CA3256 IC
switch and amplifier discussed provide an excellent choice
for a cost-effective high-performance video-switch amplifier,
by taking advantage of the complementary features of both
high-speed CMOS and bipolar integrated circuits.
CA3256
8-11
FIGURE 8. AN 8-TO-1 VIDEO SWITCH AMPLIFIER USING TWO
A
B
C
CA3256 DEVICES
CH
1
2
3
4
5
6
7
8
CH
5-8
CH
1-4
CH 5
NC
TRUTH TABLE
V
V
V
V
V
V
V
V
C
0
0
0
0
1
1
1
1
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN8
C
EN
1
2
3
4
5
A
B
A
B
C
EN
1
2
3
4
5
1
CA3256
2
CA3256
A
0
0
1
1
0
0
1
1
GND
GND
+
+
-
-
V+
V+
V-
V-
+12V
-5V
+12V
-5V
B
0
1
0
1
0
1
0
1
V
OUT