455 kHz IF WITH AF COMPRESSOR

Description: A combination of an intermediate frequency (IF) amplifier, audio compressor, tunable audio filter, and audio output system operates from a single supply. The compressor and filter each utilize N5558V dual operational amplifiers or equivalent units. The tuning range of the filter spans approximately 500 to 2000 Hz. The IF input is connected directly to pin 2 of the LM373H. A coupling capacitor is employed to prevent pin 2 from shorting to ground and damaging the integrated circuit.

The described circuit integrates multiple functions essential for audio processing in communication applications. The IF amplifier is responsible for amplifying the received signal, ensuring that it is at a sufficient level for further processing. The audio compressor dynamically adjusts the audio signal's amplitude, enhancing the overall sound quality by reducing the dynamic range. This is particularly useful in communication systems where consistent audio levels are crucial for intelligibility.

The tunable audio filter is designed to selectively allow frequencies within the range of 500 to 2000 Hz, which is typical for voice signals. This filter can be adjusted to target specific frequencies, thereby improving the clarity of the audio output. The use of dual op-amps, such as the N5558V, provides the necessary gain and bandwidth while maintaining low distortion levels.

The connection of the IF input to pin 2 of the LM373H is critical for the circuit's operation. This pin typically serves as a comparator input, allowing the circuit to process the amplified IF signal accurately. The inclusion of a coupling capacitor at this stage is a protective measure, ensuring that any DC offset does not affect the operation of the LM373H, which could lead to circuit malfunction or damage.

Overall, this combination of components creates a robust audio processing system suitable for miniature communication receivers, enhancing signal quality while ensuring operational reliability. The design considerations reflect a balance between performance, efficiency, and component selection, making it appropriate for various applications in the field of electronics.Combination of IF amplifier, audio compressor, tunable audio filter, and audio output system operates from single supply. Compressor and filter each use N5558V dual opamps or equivalent units. Tuning range of filter is about 500 to 2000 Hz. IF input goes directly to pin 2 of LM373H. Use coupling capacitor to prevent shorting pin 2 to ground and dam aging IC. -R. Megirian, Design ldeasfor Miniature Communications Receivers, Ham Radio, April 1976, p 18-25.