We found this circuit in the National Semiconductor's Linear Applications Handbook of 1994. The circuit uses an operational transconductance amplifier.
The LM380 is not a modern component and in some cases not easy to find. But if you have one you...
We found this circuit in the June 1992 issue of Radio Electronics magazine. The sensor is a common...
I found this circuit in a documentation about thyristors from the 70s. The circuit uses a diac...