The circuit is from 1968, but we can use a modern one like the 741. The symmetrical power supply voltage (two batteries or source) can be from 9 to 12 V.
This circuit, which uses components still common today, was found in a 1997 documentation. It...
This circuit with its light source was found in American documentation two years 70. Or...
This circuit was found in a Philips documentation from 1966. The circuit provides 1 mW with a...