Semiconductor Group

45

TDA 5940-2

Circuit Description

Video IF Section

The video IF section incorporates a four-stage, capacitively coupled, symmetrical and controlled

amplifier, a limiter with selection and a mixer for quasi-synchronous demodulation of negative

modulated IF signals followed by a video output amplifier. The video demodulator output and the

SCART-switch input are connected by means of a sound trap. The SCART switch has two inputs

(for signals from video demodulator and SCART socket) and two outputs (SCART socket and TV

output). Parallel to the video output amplifier the video signal is used for generating the AGC

voltage. The control circuit is designed on the integralaction AGC principle, employing a noise-free

peak value detector. A delayed tuner AGC voltage with positive control direction is derived from the

AGC -voltage via a threshold amplifier that is set by means of an external potentiometer.

Sound IF Section

The sound IF section incorporates a five-stage, symmetrical limiter amplifier followed by a PLL

demodulator. The AF section contains an analog switch for the Full-SCART interface and a volume

control with AF output.