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Bipolar transistors
Reading: Singh chapter 7 or Sze chapter 5 or Thuselt 5.1 - 5.5
For the exam:
- know the forward active, reverse active, cut-off, and saturation operation modes of a bipolar transistor.
- know how the emitter, base, and collector are doped and why.
- know what the Ebers-Moll model is and how it is derived.
- know what the Early effect is.
- be able to explain how a bipolar transistor works and why the base must be thin.
- be able to describe a heterojunction bipolar transistor and explain what advantages it has over an ordinary bipolar transistor.
Resources:
- Semiconductor Research Leading to the Point Contact Transistor, John Bardeen, Nobel Prize 1956 (pdf).
- Transistor Technology Evokes New Physics, William B. Schockley, Nobel Prize 1956 (pdf).
- Surface Properties of Semiconductors, Walter H. Brattain, Nobel Prize 1956 (pdf).
- Quasi-Electric Fields and Band Offsets: Teaching Electrons New Tricks, Herbert Kroemer, Nobel Prize in Physics 2000.
- Double Heterostructure Concept and its Applications in Physics, Electronics and Technology, Zhores I. Alferov, Nobel Prize in Physics 2000.
Problems
1. pnp transistor
2. Minority charge distribution in a BJT
3. In a n+pn bipolar transistor, VBE = 0.5 V and VBC = 0.5 V. What mode of operation (forward active, cut-off, ...) is this transistor in? Sketch the minortity carrrier profile in the device.
4. How does the base transport factor B depend on the width of the base Wb and the diffusion length in the base Lb. How should the transistor be doped to maximize B?
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