HA11560 Datasheet, PDF (7/10 Pages) Hitachi Semiconductor – VCR/VDP RF Modulator

HA11560FP/T
Audio Modulator
Pins 4 and 5 make up the reference oscillator for
the 4.5 MHz audio modulator. Pin 4 is the
oscillator’s reference bias source. A 15 pF
capacitor must be used for C3 at pin 4 to cut the ac
signal. The oscillation frequency is determined by
an external tank circuit.
An external cuppling capacitor is not required
when pin 6, which is the audio input pin, is almost
equal to ground potential and the audio input
signal dc level is ground potential. The ground
potential of the input pin results in a circuit
configuration that reduces pin 6 voltage
fluctuations and suppresses popping noise.
V_CC
200
2k
Audio oscillator
Audio amplifier
100
4
5
C3
T1
15 p
100 k
6
R5
330
Audio input
Figure 5 Audio Modulator Interface Circuit
7