This current meter with many scales was found in a 80s American documentation. The operational amplifier is from that time, uncommon nowadays.
In the figure we have a typical polarization circuit for MOSFETs with a high impedance...
Found ina 1970 American documentation this fast-reading circuit uses a photodiode. Transistors...
Found in a 1970's Radio Electronics, this circuit uses a triac to switch loads on the AC network. This...