This circuit is from a Radio Electronics magazine from August 1974. It used one of the first photomultiplier tubes that was to be powered by high voltage. The power came from the mains.
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...