This is a precision half-wave rectifier, suggested by Texas Instruments. Diodes are commonly used, and resistors can have signal values. The power supply must be symmetrical.
The purpose of this circuit, found in a documentation for radio amateurs in 1974, is to amplify noise...
This circuit was obtained in an old American documentation. The integrated circuit used is...
This is a Japanese commercial radio from the 60s. The circuit is listened to by phone and is...