Lecture 26 - BJT Introduction

# Lecture 26 - BJT Introduction - Bipolar-Junction...

This preview shows pages 1–4. Sign up to view the full content.

1 EE360 – Lecture 26 Bipolar-Junction Transistors: Introduction Objective: To conceptually understand how BJTs function. Questions to be answered: • What is a BJT and how do we make one? • What are the modes of operation? • How do we describe the electrostatics of a BJT? • How does a BJT operate conceptually? EE360 – Lecture 26 Device Types pnp npn • Emitter usually heavily doped (i.e. N AE = 10 18 cm -3 ) • Base more lightly doped (i.e. N DB = 10 15 cm -3 ) • Collector even more lightly doped (i.e. N AC = 10 14 cm -3 ) • New notation: N AE = emitter acceptor concentration • Base is “narrow,” or else we would just have two pn junction diodes. From Pierret, pg. 372

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 EE360 – Lecture 26 Circuit Symbols and Conventions • One way to remember the symbols: pnp = p ointing in p roudly npn = n ot p ointing in pnp npn From Pierret, pg. 372 EE360 – Lecture 26 Circuit Symbols and Conventions • Voltages and currents: – Subscripts indicate polarity (first subscript is positive) – Currents defined so that they are positive in the most common operating mode pnp npn From Pierret, pg. 372
3 EE360 – Lecture 26 Currents and Voltages: Immediate Observations • Current into device = current out of device: I E = I C + I B • Total voltage drop around a loop must be zero: V EB + V BC + V CE = 0 • We only need to find two currents and two voltages to describe the device pnp BJT From Pierret, pg. 372 EE360 – Lecture 26

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 04/20/2008 for the course EE 360 taught by Professor Hastings during the Spring '08 term at Kentucky.

### Page1 / 11

Lecture 26 - BJT Introduction - Bipolar-Junction...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online