Comparison of Power MOS and Bipolar Power Transistors

MOS	BIPOLAR
Majority-carrier device	Minority-carrier device
No charge-storage effects	Charge stored in the base and collector
High switching speeds, less temperature sensitive than bipolar devices	Low switching speed, temperature sensitive
Drift current (fast process)	Diffusion current (slow process)
Voltage Driven	Current Driven
Purely capacitive input impedance; no DC current required	Low input impedance; DC current required
Simple drive circuitry	Complex drive circuitry (resulting from high base current requirements)
Predominently negative temperature coefficient on resistance	Positive temperature coefficient of collector current
No thermal runaway	Thermal runaway
Devices can be paralleled with some precautions	Devices cannot be easily paralleled because of V_BE matching problems and local current concentration
Less susceptible to second breakdown	Susceptible to second breakdown
Square-law I-V characteristics at low current; linear I-V features at high current	Exponential I-V characteristics
Greater linear operating and fewer harmonics	More intermodulation and cross-modulation products
Low on-resistance (low saturation voltage) because of conductivity modulation of high resistivity drift region	High on-resistance and therefore larger conduction loss
Drain current proportional to channel width	Collector current approximately proportional to emitter stripe length and area
Low transconductance	High transconductance
High breakdown voltage as the result of a lightly doped region of a channel-drain blocking junction	High breakdown voltage as the result of a lightly doped region of a base collector blocking junction