We find this circuit in American documentation from the 1980s. It consists of a frequency folder using a varicap. The capacitors and coils depend on the frequency of operation.
In the figure we show how to use an LM324 as a voltage comparator the reference voltage is...
We found this circuit in a 1964 Electronic Design. It provides 0.5 V signals from 4 kHz...
This circuit is from a 1992 documentation, but the components used can still be easily assembled. The...