Overvoltage Indicator (CB22007E)

Using a CA3130 operational amplifier, this circuit drives an LED when the voltage exceeds the value set in VR1.

Noise Reducer (CB19824E)
The integrated circuit used in this configuration for noise reduction on FM radios is not common...
Electronic doorbell (CB25029E)
This circuit was found in the April 1984 issue of Radio Electronics magazine. The integrated...
High Input Impedance Stage (CB13397E)
We found this circuit in a 1977 National Semiconductor Databook. The circuit can use other FETs...