Back in the 1960s, I worked with Joe, a good technician who was very analytical. He told me he had put in many months of study to figure out how to bet on horse races. He analyzed ...

In the early days, PNP bipolar transistors were common, but the bulk of circuits you see today use NPN transistors. As [Aaron Danner] points out, many people think PNP transistors are “backward ...

T1 is the Darlington high gain PNP transistor that drives two Infrared LEDs. Resistor R4 is the pull up resistor that keeps the base of T1 high for its proper working. By changing R2 with a 4.7K ...

I used a Darlington PNP transistor to keep current into the LM334 minimal. I used a high-current, high-efficiency LED. It was surface-mount, so I used the same trick to solder it on its side to ...