This circuit can be used to test up to three LEDs at once, connected in series. You can easily increase that number by using a higher supply voltage. If you do so, you should allow 2.7 V for each ...
The circuit has been designed for transistors to determine whether the pin is emitter, base or collector as well as the type if NPN or PNP polarity, and can also be used in testing diodes. 4011 – a ...