TDA4482-D

This TDA4482-D configuration permits high-quality processing of audio carriers for FM-sound standards, providing separate inputs for the video and audio carrier. The audio carrier signal is passed to two multiplying mixer arrangements via a 3-stage variable wideband amplifier with led level output signals. One mixer generates the gain-control signal. The second mixer operates as an intercarrier demodulator and supplies the intermediate AF carrier. The video carrier signal required from the intercarrier is decoupled in a prelimited and selected form from the demodulator tank of the intermediate video frequency circuit (TDA4453 or TDA4439) and led to the intercarrier mixer via a limiting amplifier. Depending on the system, the Nyquist range of the IF input filter in the video channel affects the attainable AF signal-to-noise ratio.

The audio PM IF TDA4482-D carrier reaches the quadrature demodulators via an inter-connected IF filter and subsequent limiting amplifier. The resulting AF signals are led via a low-pass amplifier with increased level to the buffered output stages. Switching can take place with TTL equivalent levels.