1. NAME OF FACULTY : MR. Harekrishna Avaiya DEPARTMENT: E.C. (PPI-1ST)

2. History Transistor Types BJT: A bipolar (junction) transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications FET :The field-effect transistor (FET) relies on an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material Power transistors Sub: BE Topic: Transistors

3.  A Transistor is an electronic device  composed of layers of a semiconductor  material which regulates current or  voltage flow and acts as a switch or gate  for electronic circuit. Sub: BE Topic: Transistors

4.  John Pierce –supervised the Bell Labs team which built the first transistor (1947)  First Solid State Transistor – (1951) Gordon K. Teal (left) and Morgan Sparks at Bell Laboratories, 1951  Akio Morita, who founded a new company named Sony Electronics that mass-produced tiny transistorized radios (1961) Sub: BE Topic: Transistors

5.  Switching  Amplification  Oscillating Circuits  Sensors Sub: BE Topic: Transistors

6. N-type Semiconductor has an excess of electrons  – Doped with impurity with more valence electrons than silicon P-type Semiconductor has a deficit of electrons (Holes)  – Doped with impurity with less valence electrons than silicon Sub: BE Topic: Transistors

7.  - Bringing P and N Semiconductors in contact  P TypeN Type  - Creation of a Depletion Zone Sub: BE Topic: Transistors

8.  Applying –Voltage to Anode increases  Barrier Voltage & Inhibits Current Flow Applying Voltage to Cathode Barrier Voltage to Anode allows current flow Forward Biased => Current Sub: BE Topic: Transistors

9. NPN: transistor where the majority current carriers are electrons The majority current carriers in the PNP transistor are holes Sub: BE Topic: Transistors

11. Semiconductor device First Active circuit element - gain > 1 Discuss the Bipolar Junction Transistor only See Simpson Chapter 5 for more detail. Sub: BE Topic: Transistors

12. NPN Bipolar Junction transistor shown (PNP also possible) 3 terminals: Emitter, Base, Collector Contains 2 p-n junctions: emitter-base junction, collector-base junction Can be thought of as two back-to-back diodes, but operating characteristics are very different Base region (P-type here) must be thin for transistor action to work Base Emitter Collector Sub: BE Topic: Transistors

13. Use 2 voltage supplies to bias the two junctions (forward or reverse) 3 basic modes: cutoff, active and saturation, correspond to three different bias conditions. Base Emitter Collector “OFF” “ON” Sub: BE Topic: Transistors

14. Collector-Base junction is reverse biased Emitter-Base junction is forward biased i C = β i B ( β =100 - 500) Active circuit element - gain > 1 !! How does collector current flow when collector-base junction is reverse biased? Emitter CollectorBase + - iCiC iBiB iEiE V CE V BE Sub: BE Topic: Transistors

15. What's happening? Emitter-base is forward biased; collector-base reverse biased. Forward bias of emitter injects electrons into thin base region Majority shoot through the base into the collector region where they encounter the voltage source on the collector and produce a current. Electrons combine with holes in the base region and form negative ions which impede the flow Drawing off negative charge via the base lead reduces this effect (“making the base smaller”) - so the base current controls the flow of electrons into the collector Nobel Prize 1956; Shockley, Bardeen & Brattain Direction of current flow + - Sub: BE Topic: Transistors

16. BJTs are not symmetric devices Doping and physical dimensions are different for collector and emitter Collector largest, connected to heat sink as most power dissipated there Emitter region smaller, and more heavily doped to provide an abundance of charge carriers Base region is very thin (~50nm) to enhance probability that electrons will cross it PNP devices also exist - diode senses are reversed, so bias voltage polarities must also be reversed Sub: BE Topic: Transistors

17. Emitter CollectorBase + - iCiC iBiB iEiE V CE V BE Simplest model for low frequencies (DC condition) "Ebers-Moll". Relates collector current I C to base-emitter voltage V BE : I S =Saturation Current Similar to Diode Law Recall I B =I C / β V BE ICIC Collector current is controlled by the base-emitter voltage V BE Sub: BE Topic: Transistors

18. Note labelling scheme: i C =I C +i c "Common emitter" configuration Sub: BE Topic: Transistors