Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
This circuit is from 1980s documentation. The maximum operating frequency is 3.5 MHz. The current of...
This circuit is from a publication from the 70s. The tunnel diode is the critical component, and...
This circuit was obtained from an English magazine from 1980, but as it uses components that can...