Chapter 4 DC Biasing-BJTs - Centurion University
Chapter 4DC Biasing–BJTs
BiasinggBiasing: The DC voltages applied to a transistor inorder to turn it on so that it can amplify the AC signal.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Operatingpg PointThe DC inputestablishes anoperating orquiescent pointcalled the Q-pointpoint.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
The Three States of Operationp Active or Linear Region OperationBase–Emitter junction is forward biasedBase–Collector jjunction is reverse biased Cutoff Region OperationBBase–EmitterE itt junctionjti isi reverse biasedbi d Saturation Region OperationBase–Emitter junction is forward biasedBase–Collector jjunction is forward biasedElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
DC Biasingg Circuits Fixed-bias circuitEmitter-stabilized bias circuitCollector emitter loopCollector-emitterVoltage divider bias circuitDC bias with voltage feedbackElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Fixed BiasElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
The BaseBase-Emitter LooppFrom Kirchhoff’s voltagelaw: VVCC – IBRB – VBE 0Solving for base current:IB V CC V BERBElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Collector--Emitter LoopCollectorpCollector current:I C βI BFrom KirchhoffKirchhoff’ss voltage law:VCCE VCC I C R CElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
SaturationWhen theWhth transistorti t isi operatingti ini saturation,tticurrenttthrough the transistor is at its maximum possible value.I Csat V CCRCVCE 0 VElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Load Line AnalysisThe end points of the load line are:ICsatIC VCC / RCVCE 0 VVCEcutoffVCE VCCIC 0 mAThe Q-point is the operating point: where the value of RB sets the value ofIB that sets the values of VCE and ICElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Circuit Values Affect the QQ--Pointmore Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Circuit Values Affect the QQ--Pointmore Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Circuit Values Affect the QQ--PointElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Emitter--Stabilized Bias CircuitEmitterAdding a resistor(RE) to the emittercircuit stabilizesthe bias circuit.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Base--Emitter LoopBaseFrom Kirchhoff’s voltage law: VCC - I E R E - VBE - I E R E 0Since IE (β 1)IB:VCC - I B R B - (β 1)I) BRE 0Solving for IB:IB VCC - VBER B (β 1)R EElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Collector--Emitter LoopCollectorFrom Kirchhoff’s voltage law:I R V I R V 0E ECE C CCCSince IE IC:VCE VCC – I C (R C R E )Also:VE I E R EVC VCE VE VCC - I C R CVB VCC – I R R B VBE VEElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Improved Biased StabilityStability refers to a circuit condition in which the currents and voltageswill remain fairly constant over a wide range of temperatures andtransistor Beta (β) values.Adding RE to the emitter improves the stability of a transistor.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Saturation LevelThe endpoints can be determined from the load line.VCEcutoff:ICsat:VCE VCCI C 0 mAElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyVCE 0 VIC VCCRC RECopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Voltage Divider BiasThis is a very stablebias circuit.The currentsTht anddvoltages are nearlyindependent of anyvariations in β.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Approximate AnalysisWhere IB I1 and I1 I2 :VB R 2 VCCR1 R 2Where βRE 10R2:VEIE REVE VB VBEFrom Kirchhoff’s voltage law:VCE VCC I C R C I E R EIE ICVCE V CC I C (R C R E )Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Voltage Divider Bias AnalysisTransistor Saturation LevelV CCI Csat I Cmax RC RELoad Line AnalysisCutoff:Saturation:VCE VCCI C 0mAElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyVCCIC RC REVCE 0VCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
DC Bias with Voltage FeedbackAnother way toimprove the stabilityof a bias circuit is toadd a feedback pathfrom collector tobase.IIn thithis bibias circuiti itthe Q-point is onlyslightly dependent onthe transistor beta, β.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Base--Emitter LoopBaseFrom Kirchhoff’s voltage law:VCC – I ′C R C – I B R B – VBE – I E R E 0Where IB IC:I' I I IC C BCKnowing IC βIB and IE IC, the loopequation becomes:VCC – β I B R C I B R B VBE β I B R E 0Solving for IB:IB VCC VBER B β(R C R E )Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Collector--Emitter LoopCollectorApplying Kirchoff’s voltage law:IE VCE I’CRC – VCC 0Since I′I′C IC and IC βIB:IC(RC RE) VCE – VCC 0Solvingg for VCE:VCE VCC – IC(RC RE)Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Base--Emitter Bias AnalysisBaseTransistor Saturation LevelV CCI Csat I Cmax RC RELoad Line AnalysisCutoff:VCE VCCI C 0 mAElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskySaturation:VCCI C R RCEVCE 0 VCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Transistor Switching NetworksTransistors with only the DC source applied can be usedas electronic switches.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Switchingg Circuit CalculationsSaturation current:I Csat VCCRCTo ensure saturation:IB I Csatβ dcEmitter-collector resistanceEmitterat saturation and cutoff:R sat VCEsatI CsatC tR cutoff VCCI CEOElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Switching TimeTransistor switching times:t on t r t dt off t s t fElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Troubleshooting Hints Approximateppvoltagesg– VBE .7 V for silicon transistors– VCE 25% to 75% of VCCTest for opens and shorts with an ohmmeter.Test the solder joints.Test the transistor with a transistor tester or a curve tracer.tracerNote that the load or the next stage affects the transistor operation.Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
PNP TransistorsThe analysis for pnp transistor biasing circuits is the sameas that for npn transistor circuits. The only difference is thattheh currents are flflowingi ini theh oppositei direction.diiElectronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis NashelskyCopyright 2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 All rights reserved.
Chapter 4 DC Biasing-BJTs. Biasing Biasing: TThe DC voltages applied to a transistor in order to turn it on so that it can amplify the AC signal. . DC Bias with Voltage FeedbackDC Bias with Voltage Feedback Another way to improve the stabilityimprove the stability of a bias circuit is to
DC Biasing Circuits Most common four common-emitter biasing circuits are given below 1.Fixed-Bias Circuit 2.Emitter-Stabilized Bias Circuit 3.Voltage Divider Bias Circuit 4.DC Bias with Voltage Feedback Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-2017 5 / 59 DC Biasing of BJTsDC Biasing Circuits Fixed-Bias Circuit
DC Biasing of BJTsDC Biasing of BJTs DC Biasing Biasing refers to the DC voltages applied to the transistor to put it into active mode , so that it can amplify the AC signal. The DC input establishes an operating point or quiescent point called the Q-point . Proper DC biasing should try to set the Q-point towards the middle of active region, e.g.,
Biasing Circuit Biasing Circuit Biasing circuit uses same V . Very practical methods for biasing the BJTs (or MOSFETs) can be used . 4. Common Emitter with R E / Common Source with R S 5. Cascode (actually CE:CB or CS:CD cascade) 6. Darlington (special CE:CE or CS:CS cascade)
predefined DC sources and rest of the design are related with these sources i.e., global biasing. Our method separates the nonlinear components from the limitations of global biasing [3]. Verhoeven [6] presents a method for biasing amplifiers and in this method, biasing design is performed linearly until the end except for the transistors.
What is transistor DC biasing ? Biasing is selec3on of opera3ng point (Quiescent point) to operate a transistor in a desired region (Ac3ve, cutoff, satura3on) Biasing Circuit: The circuitry which provides the necessary condi3ons of transistor biasing is known as biasing circuit.
Chapter 4 : DC Biasing - BJTs Lec04_p1 Munther N. Thiyab 2019-2020. 1 University of Anbar College of Engineering Dept. of Electrical Engineering Fundumental of Electronic I Msc: Munther Naif Thiyab Biasing Biasing: The DC voltages applied to a transistor in order to turn it on so that it can amplify the AC signal.
Part One: Heir of Ash Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26 Chapter 27 Chapter 28 Chapter 29 Chapter 30 .
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