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Video ICs
VCR audio signal processing system
BH7775K
The BH7775K is an audio signal processing system IC that includes a peak-noise reduction (PNR) processor, an FM
modulator / demodulator circuit, an input / output switcher, an automatic FM detector circuit, an FM band-pass filter,
a normal-audio circuit, a regulator circuit, and automatic adjusting circuits (VCO and BPF).
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Applications
VHS Video cassette recorders
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Features
1) Operates off dual ± power supply which allows a
large reduction in the number of coupling capacitors
required. A built-in regulator makes it easy to con-
struct a power supply system.
2) A built-in 2-wire serial control decoder circuit allows
serial control of the internal mode settings.
3) Automatic adjusting VCO and BPF circuits that use
the color signal subcarrier frequency (NTSC:
3.579545MHz and PAL: 4.433619MHz) ensure sta-
ble adjustment that is not effected by stress when
the chip is mounted, or variations over time.
4) 4-input switcher (turner, BS, and line 1 and 2).
Output switch with built-in STEREO / LEFT / RIGHT
switching, Hi-Fi / MIX / NORMAL switching, and BS
monitor functions.
5) The PNR processor and FM modulation / demodula-
tion circuit provide reverse characteristics at record-
ing and playback. Also, carrier frequency adjustment
and FM de-emphasis / playback level adjustment
have been combined.
6) Built-in FM band-pass filter connects directly to the
playback amplifier and excels at attenuation of the
other channel. The FM recording output circuit has a
high-performance high-frequency cutoff filter that
produces a sine wave output.
7) Switching noise is reduced by a slope-control type
differential compensation circuit.
8) Built-in envelope detector circuit and noise-detecting
automatic FM detector circuit.
9) Built-in normal-audio signal processing circuit that
allows SP / LP / EP equalizer switching. Control ter-
minal provided for use with the BA7755AF high-volt-
age head switcher.