This 90s Motorola circuit from, has current limiting foldback. The power transistor is from the era, and equivalents can be used. The output is 250 V.
Using NTCs or LDRs as sensors, the frequency of this circuit depends on the temperature or the...
This circuit was found in a Popular Electronics from 1991. The transistor could be the BC548. The...
This circuit was found in a 1994 publication. It can receive signals from the 3 to 20 MHz band,...