The presented circuit uses a PNP transistor, which can be the BC558. Observe the polarity of the supply. The circuit is suggested by Texas Instruments opto-electronic documentation.
The signal from this circuit found in a 1968 Electronics World is sinusoidal and depends on the...
Found in the March 1974 Radio Electronics magazine, this circuit is designed to measure the level...
This circuit, found in Texas Instruments documentation from the 90's, provides a voltage reference of...