Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar...
Transcript of Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar...
![Page 1: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/1.jpg)
Unit – 2Semiconductor Devices
Lecture_2.3
Bipolar Junction Transistor (BJT)
![Page 2: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/2.jpg)
Bipolar Junction Transistor (BJT)
• 3 terminal, active, electronic device.
• Bipolar - Current is contributed both by majority and minority charge carriers.
• Similar to vacuum tubes but smaller in size.
• Used in computers, satellites, communication systems, etc..• Amplifier
• Oscillator
• Switch
![Page 3: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/3.jpg)
Construction of BJT
• Silicon or germanium crystal• PNP thin layer of N-type material between 2 P-type materials.
• NPN thin layer of P-type material between 2 N-type materials.
• Emitter (E), Base (B) and Collector (C).• E is heavily doped, injects large carrier to B.
• B is lightly doped, very thin; passes carriers from E to C.
• C is moderately doped.
• Arrow on E specifies, direction of current flow.
![Page 4: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/4.jpg)
Construction of BJT
![Page 5: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/5.jpg)
Transistor Biasing
• EB junction is Forward Biased.
• CB junction is Reverse Biased.
• Forward biasing causes current flow from E to C through B.
• All emitter current flows through collector.
![Page 6: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/6.jpg)
Operation of NPN Transistor
• EB junction is forward biased.
• e- from E crossover B.
• e- combines with holes in B which is lightly doped with P-type impurity.
• As a result base current 𝐼𝐵 decreases.
• Remaining e- constitutes collector current 𝐼𝐶 .
• Internal Emitter current, • 𝑰𝑬 = − 𝑰𝑪 + 𝑰𝑩
• External circuit Emitter current,• 𝑰𝑬 = 𝑰𝑪 + 𝑰𝑩
![Page 7: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/7.jpg)
Operation of PNP Transistor
• EB junction is forward biased.
• Holes from E, cross B to reach C.
• Holes combines with e- in B which is doped lightly with N-type impurity.
• As a result base current 𝐼𝐵 decreases.
• Remaining holes constitutes collector current 𝐼𝐶 .
• Internal Emitter current, • 𝑰𝑬 = − 𝑰𝑪 + 𝑰𝑩
• External circuit Emitter current,• 𝑰𝑬 = 𝑰𝑪 + 𝑰𝑩
![Page 8: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/8.jpg)
Types of transistor configuration
Configuration Common Terminal Input Terminal Output Terminal
CE Emitter (E) Base (B) Collector (C)
CB Base (B) Emitter (E) Collector (C)
CC Collector (C) Base (B) Emitter (E)
![Page 9: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/9.jpg)
CB Configuration – Circuit diagram
![Page 10: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/10.jpg)
CB Configuration – Input Characteristics
• Starting from zero, 𝑉𝐶𝐵 is kept constant.
• 𝐼𝐸 is measured by increasing 𝑉𝐸𝐵, functions as forward biased PN diode.
• Early effect – as reverse bias to CB junction is increased, base width decreases and space charge between C & E increases.
• Punch through – at larger biasing voltages, base width = 0; voltage breakdown of transistor occurs.
![Page 11: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/11.jpg)
CB Configuration – Output Characteristics
• 𝐼𝐸 is kept constant by adjusting 𝑉𝐸𝐵.
• 𝐼𝐶 is measured by increasing 𝑉𝐶𝐵 for each value of 𝐼𝐸.
• 𝐼𝐶 is independent of 𝑉𝐶𝐵, 𝐼𝐶 flows for 𝑉𝐶𝐵 = 0.
![Page 12: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/12.jpg)
CE Configuration – Circuit diagram
![Page 13: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/13.jpg)
CE Configuration – Input Characteristics
• Starting from zero, 𝑉𝐶𝐸 is kept constant.
• 𝐼𝐵 is measured by increasing 𝑉𝐵𝐸, functions as forward biased PN diode.
![Page 14: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/14.jpg)
CE Configuration – Output Characteristics
• 𝐼𝐵 is kept constant by adjusting 𝑉𝐵𝐸.
• 𝐼𝐶 is measured by increasing 𝑉𝐶𝐸 from zero.
• Saturation region, both junctions are FB; for increase in 𝐼𝐵, there is no large change in 𝐼𝐶 .
• Cut off region, below 𝐼𝐵 = 0, both junctions are RB; open circuit between C & E; off state.
• Active region, EB junction is FB & CB junction is RB; linear amplification; short circuit; on state.
![Page 15: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/15.jpg)
CC Configuration – Circuit diagram
![Page 16: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/16.jpg)
CC Configuration - Characteristics
Input Characteristics Output Characteristics
Characteristics are same as CE Configuration
![Page 17: Unit – 2 Semiconductor Devices · 2019. 9. 11. · Semiconductor Devices Lecture_2.3 Bipolar Junction Transistor (BJT) Bipolar Junction Transistor (BJT) •3 terminal, active, electronic](https://reader036.fdocuments.in/reader036/viewer/2022071415/610fa97ff909d517522c7dce/html5/thumbnails/17.jpg)
Comparison of CB, CE & CC Configuration