Using a common crystal diode and a 741, this circuit can be used to detect microwaves. The circuit is from old documentation and the switch selects the gains.
May 2017 - Panasonic's new APS1 series of optical couplers with 3 750 V insulation and up to 50...
The operational ones used in this circuit are not common today, but the circuit can be implemented with...
The operational amplifier used in this circuit from a 1970s publication is no longer easily found...