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.
This circuit allows you to use a calculator as a timer by directly activating a sum key with...
This “Half adder” circuit uses NAND gates from a 7400. The power supply must be 5 V. ...
ECL logic circuits can operate at very high frequencies. This circuit was obtained from a 1977...