This circuit consists of an inverter powered by only 4.5 V. The circuit is from a 1967 Mullard documentation. No information was provided on the transformer winding. Capacitors can be 1.5 nF x 3 kV.
This circuit uses a CA3140, an operational amplifier with FETs in the input stages. Equivalent can be...
This circuit is indicated to operate from high impedance sources as piezoelectric transducers....
This circuit also detects IR, providing LED indication. The circuit is used to indicate humidity in...