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.
This circuit was found in a 1980s American schematic. Transistors can be modern equivalents. The...
Raytheon's RC4858 amplifier is like the 741. This circuit was obtained in an old circuit manual. The...
This circuit is from a 1974 technical documentation. The publication deals with applications of...