This circuit of a 1969 Electronic Design uses RTL logic. The setting can be adapted to TTL. The frequency is given by the crystal.
This circuit is from old documentation having a gain of approximately 35 dB at 1 kHz with 2.2 mV...
Voltage comparators, such as those in the LM139/239/339 series, consist of devices that can be...
This old configuration using a germanium transistor was designed to operate with variable...