Comparison of Power MOS and Bipolar Power Transistors
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 simply paralleled because of VBE 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 |