Using the integrated circuit 723 we found this power supply in an article in the magazine Radio Electronics from August 1971. The transistor may be a BD136 equipped with a heat sink.
We found this circuit in a 1990 documentation. The operational amplifiers are type 741 and the LED is...
We found this circuit on an Elektor from the 90s. The frequency is given by capacitor C1. The...
Found in National Semiconductor publication from the 1980s. This gain-100 circuit can be...