We found this circuit in Ferranti's 1974 transistor manual. The components are from the period. The table gives the value of C1 for different frequency ranges.
This circuit was found the Optoelectronics Sourcebook by Texas Instruments. Any phototransistor...
January 2017 - Pulse Electronics' new current sensing insulation transformers for automotive...
This circuit, found in a 1958 magazine, is for reference only, since the components are not easy...