This circuit employs an old germanium transistor. The circuit is from a 1950s publication and uses RC coupling.
This simple injector and signal follower employs a high impedance headset. Transistors can be of...
Found in a 90s Popular Electronics, this circuit uses common components. The power transistors can be...
I found this circuit in a 2005 Wireless World and it is ideal for driving high power white LEDs....