Ete411 Lec15

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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

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Ete411 Lec15

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

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