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Transistors in Parallel

Transistors in Parallel. Why connect transistors in parallel?. Connect in parallel to handle high currents Need to be closely matched for equal current sharing. Connect resistors in series with the emitters to get 45 to 55% current sharing. Dynamic Current Sharing.

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Transistors in Parallel

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  1. Transistors in Parallel

  2. Why connect transistors in parallel? • Connect in parallel to handle high currents • Need to be closely matched for equal current sharing. • Connect resistors in series with the emitters to get 45 to 55% current sharing.

  3. Dynamic Current Sharing

  4. Consider an increase in IE1 • If IE1 increases, • L1(dIE1/dt) increases • Voltage L2(dIE1/dt) increases, increasing current IE2 (shifting, or sharing the increase)

  5. Turn-on and Turn-off times During turn-on,

  6. Turn-on and Turn-off times During turn-off,

  7. Transistor Chopper limits limits

  8. Approximate Switching Waveforms

  9. Equivalent Circuit at turn-on

  10. Equivalent Circuit at turn-off

  11. At turn-off • Q1 becomes open • IL flows through CS, charging it towards VS • The capacitor voltage appears across Q

  12. When C charges to VS, Dm turns on

  13. Looks like an RLC circuit

  14. Discharge time = TS/3

  15. Insulated-Gate Bipolar Transistor IGBT Collector -- C Gate -- G Emitter -- E

  16. Output Characteristics

  17. Transfer Characteristic

  18. Structure

  19. When VGE>VT – Channel Induced Induced channel

  20. Equivalent Circuit

  21. Driver Circuit

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