Found in a 1970 EEE, this circuit uses general-purpose transistors of the time. Transistors support equivalents and the ramp time ranges from 0.1 seconds to a few seconds, depending on C1.
The basis of this circuit is a CA3130 operational amplifier. The transistor can be BC548, and the...
This circuit, found in a 73 magazine for radio amateurs, is used in radio localization. The...
This circuit is from an American magazine Popular Electronics of March 1991. The circuit produces both...