Transistors: Controlled Current Sources

A transistor is a three-port (3-pin, 3-legs, 3-terminals) electronics device where a current or a voltage signals controls the intensity of a larger current.

IGBTs/IEGTs

An Insulated Gate Bipolar Transistor, IGBT, and an Injection Enhanced Gate Transistor, IEGT, are devices that switch power on and off between a collector and emitter by controlling the voltage between the gate and emitter in the same way as MOSFET.

Comparison of Bipolar Power Transistors and Power MOSFETs

	Bipolar Power Transistor Power	MOSFET
CONCEPT	BJT	MOSFET
\1	\2	\3
Drive circuit	Drive conditions are difficult to determine because switching time varies with drive current conditions. Also, the drive circuit suffers high power loss.	The drive circuit for the voltage control of a power MOSFETs is simpler and offers lower power loss than that of a bipolar resistor.
Switching time	Due their structure, bipolar transistors have a storage time `t_stg` and therefore a longer switching time than MOSFETs.	Power MOSFETs are much faster than bipolar power transistors. Power MOSFETs have no storage time and are less affected by temperature.
Safe operating area (SOA)	Restricted due to the risk of secondary breakdown.	Restricted mainly by power dissipation (equal power lines).
Breakdown voltage (Collector-emitter, drain-source)	Bipolar power transistors are often used with a reverse current between the base and emitter. Sometimes, both `V_CES` and `V_CEX` (`V_CBO`) are rated.	The withstand voltage is limited by `V_DSS` except for trench MOSFETs operating in a reverse gate bias condition (during which the withstand voltage is restricted by `V_DSX`).
On-state voltage	Even high voltage bipolar power transistors have very low on-state voltage and generally have a negative temperature coefficient.	Low-voltage power MOSFETs have an extremely low on-state voltage. High voltage devices have a slightly higher on-state voltage. Power MOSFETs have a positive temperature coefficient, which is beneficial in connecting multiple devices in parallel.
Parallel connection	It is necessary, but difficult, to equalize the current flowing through multiple transistors connected in parallel.	Multiple power MOSFETs can be connected in parallel, but it requires a bit of care to prevent oscillation and match the switching times of the parallel devices.
Temperature stability	A certain amount of care is required because an increase in temperature causes `h_FE` to increase and `V_BE` to decrease.	Various characteristics exhibit outstanding temperature stability.