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Lecture #3 BJT Transistors & DC Biasing Instructor: Dr. Ahmad El-Banna N
ov
em
ber
2014
J-601-1448 Electronic Principals
Integrated Technical Education Cluster At AlAmeeria
© A
hmad
El-B
anna
Agenda
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Transistor Construction & Operation
Transistor Configurations
Transistor Testing & Terminal Identification
Transistor DC Bias Configurations
Design Operations
Various BJT Circuits &Troubleshooting Techniques
Practical Applications
Transistor Construction
• Basic BJT Constructions
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• Basic BJT symbols and Currents
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Transistor Operation
• Basic Operation using pnp transistor.
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• Majority and minority carrier flow of a pnp transistor.
• Biasing a transistor: (a) forward-bias (b) reverse-bias.
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BJT CONFIGURATIONS
• Common Base
• Common Emitter
• Common Collector
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Configurations: Common Base
• Notation and symbols used with the common-base configuration: (a) pnp transistor; (b) npn transistor.
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• Input or driving point characteristics for a common-base silicon transistor amplifier.
• Output or collector characteristics for a common-base transistor amplifier.
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Configurations: Common Base..
• Formulas:
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• Biasing of a CB pnp tr. in the active region:
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Configurations: Common Emitter
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• Notation and symbols used with the common-emitter configuration: (a) pnp transistor
(b) npn transistor.
• Characteristics of a silicon transistor in the common-emitter configuration:
(a) collector characteristics
(b) base characteristics.
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Configurations: Common Emitter..
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• Formulas:
• Biasing of a CE npn tr. in the active region:
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Configurations: Common Collector
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• Notation and symbols used with the common-collector configuration: (a) pnp transistor; (b) npn transistor.
• Common-collector configuration used for impedance-matching purposes. J-6
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Configurations: Common Collector..
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• Defining the linear (undistorted) region of operation for a transistor.
• Formulas:
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PRACTICAL VIEW
• Transistor Spec. Sheets
• Transistor Testing
• Transistor Casing and terminals identification
• Transistor Development
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Transistor Specification Sheets
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Transistor Specification Sheets..
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Transistor Testing using Curve Tracer
15 • Check the beta value:
Curve tracer response to 2N3904 npn transistor.
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Transistor Testing using Transistor Tester
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• Transistor testers: (a) digital meter (b) dedicated testers.
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Transistor Testing using Ohmmeter
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• Checking the forward-biased base-to-emitter junction of an npn transistor.
• Checking the reverse-biased base-to-collector junction of an npn transistor.
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Transistor Casing
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• Various types of general-purpose or switching transistors: (a) low power (b) medium power (c) medium to high power.
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Terminal Identification
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• Transistor terminal identification.
• Internal construction of a Fairchild transistor in a TO-92 package.
• Type Q2T2905 Texas Instruments quad pnp silicon transistor: (a) Appearance (b) pin connections.
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TRANSISTOR DC BIAS CONFIGURATIONS
• Fixed-Bias Configuration
• Voltage-Divider Bias Configuration
• Emitter-Follower Configuration
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• Biasing means applying of dc voltages to establish a fixed level of current and voltage. >>> Q-Point
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Fixed-Bias Configuration
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• Fixed-bias circuit. • DC equivalent ct.
• Base–emitter loop. • Collector–emitter loop.
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Fixed-Bias Configuration Example
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Fixed-Bias Configuration ...
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• Load Line Analysis
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Saturation Current
Voltage-Divider Configuration
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• Exact Analysis • Voltage-divider bias configuration.
• DC components of the voltage-divider configuration.
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Voltage-Divider Configuration
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• Approximate Analysis • Transistor Saturation
• Load-Line Analysis
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Voltage-Divider Configuration Example
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Emitter-Follower Configuration
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i/p ct
o/p ct
• dc equivalent ct
• Common-collecter (emitter-follower) configuration.
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Summary Table
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Summary Table..
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DESIGN OPERATION 30
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Design Operations
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• The design process is one where a current and/or voltage may be specified and the elements required to establish the designated levels must be determined.
• The design sequence is obviously sensitive to the components that are already specified and the elements to be determined. If the transistor and supplies are specified, the design process will simply determine the required resistors for a particular design.
• Once the theoretical values of the resistors are determined, the nearest standard commercial values are normally chosen and any variations due to not using the exact resistance values are accepted as part of the design.
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Design Operations Example
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VARIOUS BJT CIRCUITS
• MULTIPLE BJT NETWORKS
• CURRENT MIRRORS
• CURRENT SOURCE CIRCUITS • Bipolar Transistor Constant-Current Source
• Transistor/Zener Constant-Current Source
• PNP TRANSISTORS
• TRANSISTOR SWITCHING NETWORKS
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MULTIPLE BJT NETWORKS
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• R–C coupling
• Darlington configuration
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CURRENT MIRRORS
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CURRENT SOURCE CIRCUITS
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• Bipolar Transistor Constant-Current Source
• Transistor/Zener Constant-Current Source
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pnp
TRANSISTORS
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TRANSISTOR SWITCHING NETWORKS
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TRANSISTOR SWITCHING NETWORKS..
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TROUBLESHOOTING TECHNIQUES 39
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TROUBLESHOOTING TECHNIQUES • For an “on” transistor, the voltage VBE should be in the neighborhood of 0.7 V.
• For the typical transistor amplifier in the active region, VCE is usually about 25% to 75% of VCC .
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PRACTICAL APPLICATION
• BJT Diode Usage and Protective Capabilities
• Relay Driver
• Alarm System with a CCS
• Voltage Level Indicator
• Logic Gates
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Practical Application
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• BJT Diode Usage and Protective Capabilities
• Relay Driver
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Practical Application…
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• Alarm System with a CCS
• Voltage Level Indicator
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Practical Application….
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• Logic Gates
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• For more details, refer to:
• Chapter 3 & 4, Electronic Devices and Circuits, Boylestad.
• The lecture is available online at:
• https://speakerdeck.com/ahmad_elbanna
• For inquires, send to:
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