Chapter 3: Bipolar Junction Transistors Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Transistor Construction Slide 1 Transistor Construction There are two types of transistors: pnp and npn-type. Note: the labeling of the transistor: E - Emitter B - Base C - Collector Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Transistor Operation Slide 2 With the external sources (VEE and VCC) in the polarities as shown: The E-B junction is forward-biased and the B-C junction is reverse biased. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Currents in a Transistor Slide 3 Currents in a Transistor [Formula 3.1] Note that IC is comprised of two currents: [Formula 3.2] Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Common Base Configuration Slide 4 Common Base Configuration The base is common to both input (emitter – base) and output (collector – base) of the transistor. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Input Characteristics for a Common-Base Amplifier Slide 5 Input Characteristics for a Common-Base Amplifier This demonstrates the input current IE to input voltage VBE for various levels of output voltage VCB. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Output Characteristics for a Common-Base Amplifier Slide 6 This demonstrates the output current IC to an output voltage VCB for various levels of input current IE. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Operating range of the amplifier. • Cutoff Slide 7 3 Regions of Operation • Active Operating range of the amplifier. • Cutoff The amplifier is basically off. There is voltage but little current. • Saturation The amplifier is full on. There is little voltage but lots of current. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Approximations Slide 8 [Formula 3.3] [Formula 3.4] Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Ideally = 1, but in reality it is between 0.9 and 0.998. Slide 9 Alpha () Alpha () relates the DC currents IC to IE : [Formula 3.5] Ideally = 1, but in reality it is between 0.9 and 0.998. Alpha () in AC mode: [Formula 3.6] Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Transistor Amplification Slide 10 Transistor Amplification The AC input is amplified. [Fig. 3.12] IC IE so IL Ii = 10mA VL = IL * R = (10mA)(5k) = 50V Voltage Gain (AV): Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Common – Emitter Configuration Slide 11 Common – Emitter Configuration The Emitter is common to both input (base-emitter) and output (collector-emitter). The input is on the Base and the output is on the Collector. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Characteristics of Common-Emitter Slide 12 Characteristics of Common-Emitter Collector characteristics = output characteristics. Base characteristics = input characteristics. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Amplifier Currents Slide 13 IE = IC + IB IC = IE Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Actual Amplifier Currents Slide 14 Actual Amplifier Currents IC = IE + ICBO ICBO = minority collector current. This is usually so small that it can be ignored, except in high power transistors and in high temperature environments. [Formula 3.9] When IB = 0A the transistor is in cutoff, but there is some minority current flowing called ICEO. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Beta () Slide 15 In DC mode: [Formula 3.10] In AC mode: indicates the amplification factor of a transistor. ( is sometimes referred to as hfe, a term used in transistor modeling calculations) Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Determining beta () from a Graph Slide 16 Determining beta () from a Graph Note: AC = DC Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Relationship between and Slide 17 Relationship between and Both indicate an amplification factor. [Formula 3.12a] [Formula 3.12b] Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
provides a Relationship between Currents Slide 18 provides a Relationship between Currents [Formula 3.14] [Formula 3.15] Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Common – Collector Configuration Slide 19 Common – Collector Configuration The input on the Base and the output is on the Emitter. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Characteristics of Common Collector Slide 20 Characteristics of Common Collector The Characteristics are similar to those of the Common-Emitter. Except the vertical axis is IE. IE IB1 IB2 IB3 VCE Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Limitations of Operation for Each Configuration Slide 21 Limitations of Operation for Each Configuration Note: VCE is at maximum and IC is at minimum (ICmax=ICEO) in the cutoff region. IC is at maximum and VCE is at minimum (VCE max = VCEsat = VCEO) in the saturation region. The transistor operates in the active region between saturation and cutoff. Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Power of Dissipation Slide 22 Common – Base: [Formula 3.18] Common – Emitter: [Formula 3.16] Common – Collector: a Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Transistor Specification Sheet Slide 23 Transistor Specification Sheet Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Transistor Testing Slide 24 1. Curve Tracer Provides a graph of the characteristic curves. 2. DMM Some DMM’s will measure DC or HFE. 3. Ohmmeter Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.
Transistor Terminal Identification Slide 25 Transistor Terminal Identification Robert Boylestad Digital Electronics Copyright ©2002 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.