The difference between this circuit and the previous one is that it uses PNP transistors. The circuit is from Radio Electronics magazine from July 1968. The frequency depends on R1 and C1.
Found in the September 1982 issue of Radio Electronics magazine, this circuit triggers a relay...
This small two-transistor amplifier was found in the April 1994 issue of Electronics Now magazine. This...
In the figure we show how to excite a CMOS port by interrupting light on a Darlington...