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 I E1 If I E1 increases, –L 1 (dI E1 /dt) increases Voltage L 2 (dI E1 /dt) increases, increasing current I E2 (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

8. Approximate Switching Waveforms

9. Equivalent Circuit at turn-on

11. Equivalent Circuit at turn-off

12. At turn-off Q 1 becomes open I L flows through C S, charging it towards V S The capacitor voltage appears across Q

13. When C charges to V S, D m turns on

14. Looks like an RLC circuit

15. Discharge time = T S /3

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

17. Output Characteristics

18. Transfer Characteristic

19. Structure

20. When V GE >V T – Channel Induced Induced channel

21. Equivalent Circuit

22. Driver Circuit