Nte789 Integrated Circuit Stereo Multiplex Decoder

  : The NTE789 a monolithic silicon integrated circuit, is a stereo multiplex decoder intended for FM multiplex systems. This stereo multiplex decoder requires only one low?inductance tuning coil (requires only one adjustment for complete alignment), provides automatic stereo switching, energizes a stereo indicator lamp, and operates from a wide range of voltage supplies. Figure 1 shows the block diagram for the NTE789. The input signal form the detector is amplified by a low?distortion preamplifier and simultaneously applied to both signal, generated by a local voltage?controlled Oscillator (VCO), is counted down by two Frequency Dividers to a 38kHz signal and to two 19?kHz pilot?tone supplied by the FM detector is compared to the locally generated 19?kHz signal in a synchronous detector. The resultant signal controls the voltage controlled Oscillator (VC)) so that it produces an output signal to phase?lock the stereo decoder with the pilot Tone A second sychronous detector compares the locally generated 19?kHz signal with the 19?kHz pilot Tone If the pilot Tone exceeds and externally adjustable threshold voltage, a Schmitt Trigger circuit is energized. The signal from the Schmitt Trigger lights the stereo indicator, enables the 38?kHz synchronous detector, and automatically Switches the NTE789 form monaural to stereo operation. The output signal from the 38?kHz detector and the composite signal from the preamplifier are applied to a matrixing circuit from which emerge the resultant left and right channel Audio signals. These signals are applied to their respective left and right post amplifiers for amplification to a level sufficient to drive most Audio Amplifiers The NTE789 utilizes the 16?lead quad?in?line plastic package and operates
Item: NTE789
File Size : 4 KB
Pages : 3 Pages

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NTE Electronics, Inc.
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