Overvoltage Indicator (CB22007E)

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

Simple Audio Oscillator (CB18537E)
This oscillator from an old publication uses one of the first commercial transistors, the CK722....
Comparator for TTL (CB20142E)
The integrated circuit used in this configuration is not common today. The zener determines the...
Battery Charger as Power Source (CB11529E)
With good filtration, a battery charger can be used as a power source. The filter shock can be the...