The LM121 integrated circuit is no longer common in our market, with more modern equivalent versions. The circuit is from the 1994 Linear Applications Handbook by National Semiconductor.
The circuit shown is suggested by National Semiconductor's Linear Applications Handbook. The base...
This circuit uses a pickup coil to take the signal from a telephone line without contacts. The circuit...
In this circuit, the transistors are NPN for general use and the phototransistors can be replaced by...