This circuit is from a 1969 EEE magazine. The transistors are from that time, but the circuit can be implemented with modern equivalents, such as 2N2646 for Q3.
Found in Popular Electronics from the 1980s, this circuit can use more modern transistors such as...
This circuit is a utility that can be implemented with few components, without anything...
This circuit is from the Motorola LinearDatabook of 1990. It shows how it uses the LF355, 356 and...