There are numerous differences between NPN and PNP transistors, and even though both are bipolar junction transistors, ... NPNs 2N2222, 2N3904, and TIPS120 and PNPs 2N3904, and 2N3906.

The circuit uses a 2N3904 NPN transistor and a 2N3906 PNP transistor, which operate as a high-gain amplifier. See all of EDN 's Design Ideas: The 1-MΩ resistor supplies bias current. The 1-kΩ resistor ...

Meanwhile if any of you have never picked up a 2N3904 and experimented with it rather than following someone else’s circuit, ... “In an NPN transistor, ...

The actual 3-component build uses a 10 farad supercapacitor as a power source, hooked up to a 2N3904 NPN transistor and an 85-turn coil. It won’t start oscillating on its own, ...