This small control for DC motors up to approximately 1 A uses an operational amplifier that admits equivalent. The transistor can be TIP29 for currents up to 1 A or BD135 for 500 mA.
This 6-transistor transistor radio is a RCA product from the 1960s. The circuit is powered by a 9...
This variable voltage reference uses a Norton operational amplifier. The voltage is adjusted at...
This circuit is from Radio Electronics magazine, November 1974. The supply voltage depends on the...