This circuit was found in Radio Electronics from the 90s. The components used are common, and the transistors and CIs must be equipped with heat sinks.
Common operational amplifiers like the TL series, CA3140 and others can be used in this circuit...
This high-gain amplifier was found in the March 1994 issue of Electronics Now magazine. The...
We found this timer for times of a few minutes in a 1974 Ferranti transistor manual. The relay is 37...