This circuit allows you to read resistors up to 20 M ohms, converting it into voltage. The circuit is from the 90s. The operational ones used admit modern equivalents.
The TDA2613 is the mono version of the TDA1521A and has pinouts compatible with an integrated...
This circuit from an old 1978 publication uses germanium transistors but can be implemented with...
This project shows how to use an SCR in a starter circuit for a common fluorescent lamp. The SCR...