Transistors are in my opinion one of the most important discoveries of all time! We take transistors for granite, they are in everything and have made possible exponential leaps forward in research and study in so many fields. It would be impossible to characterize the impact transistors have had on our society.

Types of Transistors 

There are many types of transistors ranging from micro-amp transistors found in your computers cpu to large Insulated Gate Bipolar Transistors (IGBT) handling 200 amps and more on a single die.

There are also a wide range of package demensions and shapes for transistor suited for a variety of applications. Here is table with some general information on a few power transistors I like to use and find well suited for audio.

Package	Power	Ic	Vceo	PNP	NPN	Image
MT-200	200 watts	17A	200V	2SA1494	2SC3858
	150 watts	15A	200V	2SA1493	2SC3857
TO-92	Small Signal	200mA	40V	2N3906	2N3904
	Small Signal	600mA	160V	2N5551	2N5401
	Small Signal	100mA	45V	BC560	BC550
TO-126	12.5 watt	1.5A	80V	BD139	BD140
	20 watt	1.5A	160V	2SB649	2SD669
	20 watt	.5A	300V	MJE350	MJE340
TO-220	40 watt	3A	100V	TIP32C	TIP31C
	75 watt	10A	60V	MJE2955	MJE3055
	40 watt	7A	50-70V	2N6109	2N6292
TO-218	90 watt	15A	60V	TIP2955	TIP3055
	125 Watt	16A	160V	MJE4353	MJE4343
TO-264	150 watt	13A	230V	FJL4215	FJL4315
	230 watt	15A	350V	MJL4302a	MJL4281a
	200 watt	16A	250V	MJL21193	MJL21194
TO-3	115 watt	15A	60V	MJ2955	2N3055
				1000mw	1000mw
	250 watt	25A	140V	MJ15004	MJ15003
	300 watt	50A	120V	MJ11033	MJ11032

Bipolar Transistors

Bipolar transistors were developed out of Bell Labs 1947 invention of the point contact transistor and is mainly used as an amplifier or switch.