Description:

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.

Features:

• Requires the use of only one low–inductance tuning coil

• Automatic stereo switching

• Directly drives a stereo indicator lamp up to 100mA

• Includes driver for stereo–lamp indicator

• Operates from a wide range of power supplies: 10 to 16 volts

• Requires only one adjustment for alignment

• Switching from monaural to stereo and stereo to monaural produces no audible thumps

• Low distortion: under 0.5

• Separate dc input permits stereo defeat or enable

• High signal output: directly drives audio amplifiers

• Excellent SCA (storecast) rejection: 55dB typ.

• High audio channel separation: 40dB typ.