Transistor

	2N2222 NPN	2N3906 PNP
Union	Bipolar
Type	NPN	PNP
Encapsulation	TO-92 (Pb free)
Maximum voltage	40V
Maximum current (DC)	800mA	200mA
Current gain	>100	>300

Transistors are electronic components for signal control (current or voltage) between two jacks, depending on the signal applied to the other two jacks. As they only have three connections, one of them is common to the input and exit signals. This proportionality between the obtained signal and the given one is called Gain.

There are many types of transistors based on their gain, polarity in their jacks, maximum currents, voltages of work, the encapsulation type, size, etc.