Akai VS-2EGN

3)
Fig.
7-181
shows
the
double
balanced
detector.
(This
is
the
basic
circuit
within
the
IC)
BIAS VOLTAGE
>
> VIDEO OUT
VIF CARRIER
NW
VIF
fing atti,
DC
Fig. 7-161 Double balanced detector
ailiiinves ina
CURRENT
Fig. 7-162 VIF signal switching
When the carrier is fed to the bases of TR4 and TR8,
switched VIF signals appear at the respective collectors
(Fig. 7-162).
A VIF signal of positive only polarity, which is switch-
ed by TR4 and TR8 appears, and detected output is ob-
94
Service Manual VS-2EGN
tained at R1. (Detected output of negative polarity is
obtained at R2). Since two pairs of transistors, TR6/
TR9 and TR4/TR8 are employed for amplification, a
large video detector output can be obtained for only a
small VIF signal input.