This variable 1 A power supply with voltages up to 30 V was found in an article in June 1986 Radio Electronics magazine. The 723 IC is well known to magazine readers of the time and even today.
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...