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Ete411 Lec15

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Lecture on Introduction of Semiconductor at North South University as the undergraduate course (ETE411) …

Lecture on Introduction of Semiconductor at North South University as the undergraduate course (ETE411)
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Dr. Mashiur Rahman
Assistant Professor
Dept. of Electrical Engineering and Computer Science
North South University, Dhaka, Bangladesh
http://mashiur.biggani.org

Published in Technology , Business
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Transcript

  • 1. ETE444 :: Lec15 Dr. Mashiur Rahman Copyright: Semiconductor Physics And Devices 3rd ed. - J. Neamen
  • 2. Forward-active mode
  • 3. Injection and collection of electrons
  • 4. iE1= due to the flow of electrons injected into the base = ic ic  iE ic  iB α = Common-Base current gain β = Common-Emitter gain
  • 5. Four operation mode of bipolar transistor n
  • 6. Cuttoff mode VCB> 0 VBE < 0 B-E = reverse biased  Mejority carrier electrons from the emitter will not injected into the bias Minority carrier distribution
  • 7. Forward active mode The B-E junction becomes forward biased, an emitter current will be generated and the injection of electrons into the base results in a collector current VCB> 0 VBE > 0 Minority carrier distribution
  • 8. Inverse active The B-E forward biased and C-B VCB < 0 VBE < 0 Minority carrier distribution
  • 9. Saturation mode Both B-E and B-C junctions are forward biased and the collector current no longer controlled by the B-E voltage. VCB< 0 VBE > 0 Minority carrier distribution
  • 10. Application • Voltage amplifier by Bipolar Transistors • Switching
  • 11. Voltage amplifier by Bipolar Transistors Input sinusoidal signal voltage Sinusoidal voltage across the Rc resistor Sinusoidal collector currents Sinusoidal base currents
  • 12. Switching Raise time Storage time Fall time Circuit used for transistor switching Delay time
  • 13. Switching :: Important parameter • Current gain – lower doping in the base region is used. • Switching time – The transistor can be doped with gold to introduce midgap recombination centers and thus reduce the switching time.