This high impedance circuit was found in 1967 documentation by Ferranti. The original operational amplifier is from that time. The circuit can be implemented with modern equivalents.
This circuit is from the Motorola Linear Databook of 1990. The circuit controls a Triac from a...
The circuit shown uses the LM324, but can be implemented with other operational ones. The source...
This circuit makes use of a stroboscopic tube, a component that no longer exists today. The...