Simple Introduction To Transistor (BJT) Amplifier
Simple Introduction to Transistor(BJT) Amplifier1/10
Bipolar Junction Transistor Made out of n-type and p-type silicon There are two “flavors” of BJT’s– pnp & npnpnp TransistorTo Learn More!!EECE 332 (Semiconductors)“Why do they work?”npn TransistorFig. 28.6 from Electrical Engineering UncoveredNote: Current Directions Shown are Arbitrary!!2/10
To Learn More!!EECE 315 (Electronics)“How do they work?”BJT Operation Recall FET: current flow controlled by the gate voltage BJT: current flow controlled by the base current– Acts like a current amplifier But with the right circuitry around it can also be a voltage amplifierConceptual Model of npn TransistorCollector Base Current deflects current meter Meter linked to variable R– Controls the Collector currentÎ Voltage supply between C & Eprovides large Collector currentcontrolled by small Base currentCurrent VariableRMeterBaseEmitterFig. 28.4 from Electrical Engineering Uncovered3/10
BJT Water Model While this electrical conceptual model is good we canalso use a water modelRegulator (like scubaBase Current SpinsSmall Turbine(Turbines: no friction& no momentum)tank’s) ensures that currentflows only due to theturbine’s “suck” not thepressure differencebetween C-ELarge Turbine spins @same rate as small one BUT larger size causesmore water to flowFig. 28.5 fromElectrical Engineering UncoveredMust exceed Diode “drop”before base current flows4/10
Ic β IBCurrent Gain of BJT So the main characteristic of a BJT is its current gain(called β also called hFE) Typical β: 50 – 200 In our water model β is set by the relative size of thetwo turbines Warning a designer’s knowledge of β is almostalways imprecise!!!!– That seems to limit the usefulness but can be handledthrough proper circuit designKCL!!! Emitter Current (Collector Current) (Base Current)I E I B ICShownoppositebook’sdirection!! IB β IBRemove ( β 1) I B5/10
Main Rules of npn BJT Operation1. The B-E voltage must be at a “diode drop” of 0.7V––If not no base current flows and no collector currentLike an open switchflowsfrom collector toSo if not, the transistor is “cut off”emitter2. Collector must be more positive w.r.t. emitter3. Can’t exceed certain maximum values on IB, IC, & VCE4. When rules 1 – 3 are obeyed, IC β IBFrom The Art of Electronics, by Horowitz and Hill, Cambridge University Press6/10
Biasing a Typical BJT AmplifierBefore we can use a BJT as an amplifier we need to“set it up for use” called biasing the transistor4. Ohms law says 10Vacross RC, putting thecollector at VC 10 V20V10kΩVC 10V110kΩ1. Voltage Dividermakes this 1.7V1.7V1.0V1mA 10k Ω 10v2. Diode dropmakes this 1 V20v [10/(110 10)] 1.67v10kΩAssumes that current intobase is negligibly small1kΩ 1 mA3. Ohms law setsemitter current1.0v / 1000Ω 1mANow we can “inject” the signal we want to amplify7/10
Injecting Signal to a BJT AmplifierInput Signal is“capacitivelycoupled”10 VDCOutput Signal is“capacitivelycoupled” too!1.7 VDCSee EECE 260 Circuitsto learn methods toanalyze this ideaThe Input vin typically wiggles around a level of 0 VDC. But wewant to make the base voltage wiggle around the 1.7 VDC level.Roughly Because the cap is like an open circuit to a DC voltageit keeps these two different “DC center values” from “workingagainst” each other But it passes the input wiggles to the base!!8/10
Gain Analysis of BJT1. A small wigglingvin causes a smallwiggle ΔVB herein VB centeredaround 1.7 V10kΩ1.7V1.0V1kΩΔI E ΔV BREInversionΔVRC RC ΔI E RCRΔVC CREΔVBΔVBREGain!!3. The collector currentwiggles about thesame amount: ΔIC ΔIE.Causes the collectorvoltage to wigglearound 10V But VC goes downwhen VB goes up(inversion!!!)2. The small wiggle atthe base causes thesame amount ofwiggle here around1V ΔVE ΔVB .That causes a wigglingemitter current ΔIEaround 1mANote that the transistor’s currentgain, β, has no direct effect on the gain a good design!9/10
BJT Amplifier in Real LifeGuitar distortion boxes work (in part) by amplifying the guitarsignal before it reaches the actual amplifier this overdrivesthe amplifier to give more distortion than it would otherwiseVariation of amplifiercircuit we looked atSupplyGuitar SignalPartial Circuit for the Boss DS-1 Distortion Box for GuitarFrom Pedal Power Column by Robert Keeley, in Musician’s Hotline Magazine10/10
7/10 Biasing a Typical BJT Amplifier Before we can use a BJT as an amplifier we need to “set it up for use” called biasing the transistor 20V 10kΩ 10kΩ 1kΩ 110kΩ 1.0V 2. Diode drop makes t
Debapratim Ghosh An Introduction to Basic Electronics 11/25. Device Physics The Diode The Transistor Signals Basic Circuits Basics of the BJT BJT Working Principle Revision Quiz TheBipolarJunctionTransistor(BJT) The BJT has two p-n junctions. Since the BJT has two junctions, it can be a p-n-p or an n-p-n device.
Lecture 7. Bipolar Junction Transistor (BJT) Figure 7.9: Large signal equivalent model of the NPN BJT operating in the forward active mode. Figure 7.10: Large signal equivalent model of the NPN BJT operating in the reverse active mode. collector. — βR is in the range of
Frequency Response of BJT 1) Objectives: To study the frequency response and bandwidth of the common emitter CE-BJT, the common collector CC-BJT, and the common base CB-BJT amplifiers. 2) Introduction: Most amplifiers have relatively
BJT Models Using the BJT Model Star-Hspice Manual, Release 1998.2 14-3 Control Options Control options affecting the BJT model are: DCAP, GRAMP, GMIN, and GMINDC. DCAP selects the equation which determines the BJT capacitances. GRAMP, GMIN, and GMINDC place a conductance in parallel with both the base-emitter and base-collector pn junctions.
Standard SPICE models: Diode, BJT, MOSFET, JFET and MESFET CMC and other models: BJT –HICUM/L2/L0 MOSFET –EKV2.6 Qucs-S/Xyce Standard SPICE models: Diode, BJT, MOSFET, JFET and MESFET CMC and other models: BJT –VBIC 1.3, FBH HBT_X, HICUML0/L2, MEXTRAM. MOSFET –BSIM3, BSIM4, BSIM6, BSIM_SOI, BSIM_CMG, MVS, PSP Verilog-A ADMS generated models
BJT amplifiers of various configurations. While there is a lot more detail we can discuss in terms of BJTs and their large signal behavior, we will stop with the discussion of BJT amplifiers and continue next lecture with MOSFETs which we will focus on for the rest of the semester. – For more information on BJT circuits, read S&S 4.12 15
2.4 Clamper 24 2.5 Voltage Doubler 25 2.6 Voltage Regulator 26 3. BJT BIASING 3.1 Introduction 30 3.2 Operating Regions of Transistor 30 3.3 Modes of Operation of BJT 33 3.4 Load Line 34 3.5 Biasing 35 4. SMALL SIGNAL ANALYSIS OF BJT 4.1 Introduction 39 4.2 Transistors at Low Frequency 39 CONTENTS
However, the machining of these typically difficult-to-cut materials poses a challenge for conventional manufacturing technologies due to the high tool wear. Abrasive water jet (AWJ) machining is a promising alternative manufacturing technology for machining difficult-to-cut materials,
