GT4122 View Datasheet(PDF) - Gennum -> Semtech
Part Name
Description
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GT4122 Datasheet PDF : 5 Pages
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For normal video mixer operation, the control range (SPAN) is
usually 0 to 1V and will occur when AK=1, VREF= 0.5V and
VNOM=0.5 volts. A change in VC from 0 to 1V will then produce
an effect such that the output signal contains 100% of Channel
B when V is 0V and 100% of Channel A when V is 1 volt. For
C
C
the above conditions, the general unity gain transfer function
reduces to:
VO = VA•VC + VB•(1-VC)
Since the operation of the mixer is limited to two quadrants, no
signal inversions occur if the control voltage exceeds the
range zero to one volt in either direction. The topology is
designed so that once the control voltage reaches either end
of its range, the channel which is ON remains fully ON and the
OFF channel remains fully OFF.
-10V
RV1
200
50%
R3
GAIN
1k
R4
5.6k
RV6
Z1
1k
6.2V
+10V
-10V
C5
47
+
C1 0.1
C5
47
+
C2 0.1
R1
5 - 25pF
CCOMP
560
RV2
100
CONTROL
OFFSET
RV3
SPAN
C3 ADJUST 1K
0.1
(0.5V)
C5
0.1
VREF
ADJUST
GT4122
1 -VS
2
+VS
3 COMP
4 COS1
5 COS2
6 S1
7 VREF
8 S2
9
VC
10 GND
20
OUT
B OS2 19
-IN B 18
+IN B 17
B OS1 16
15
A OS2
-IN A 14
13
+IN A
12
AOS1
REXT 11
RV4
500
RV5
500
R2
1k
0.1
or LINK
COUT
B BLACK
LEVEL
ADJUST
+5V
C6 0.1
IC2
CLC110
1
4
ROUT 5
VIDEO OUT
8 C7 0.1
10k or
OPEN
-5V
B VIDEO INPUT
A BLACK
LEVEL
ADJUST
75
if required
A VIDEO INPUT
75
if required
CONTROL INPUT
75
if required
NOTE: C5 is used when the CONTROL VOLTAGE (VC) is derived from a power supply.
All resistors in ohms, all capacitors in µF unless otherwise stated.
Fig. 1 Test Circuit
520 - 25 - 4
4
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