We had found this circuit in a January 1961 Radio Electronics Magazine. Using it is possible to take measures from the gain of transistor with a common a multimeter.
This blinker for LEDs up to 500 mA was found in General Electric documentation from 1970....
This power supply was found in the 1996 Texas Instruments Linear Applications Manual. The circuit...
Using a CA3130 operational amplifier, this circuit drives an LED when the voltage exceeds the...