Bipolar Junction Transistor Characteristics
Bipolar Junction TransistorsBipolar Junction TransistorCharacteristicsElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction Transistors Bipolar Junction Transistor (BJT) key transistor device Formed by closely spaced pn junctions separated by narrow baseCarriers commonly injected from emitter through narrow base to collectorSmall amount of carriers recombine in base to generate small base currentEmitter injection efficiency γ also significant source of base currentGenerates large DC current gain β (or hFE) given by IC/IBBipolar transistors may be formed by using a pnp or npn deviceElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction Transistors Common emitter most widely used BJT configuration Common emitter configuration commonly used as amplifier or switch Emitter-base junction commonly forward biased and base-collectorjunction reversed biased in active mode to achieve high current gain Can create amplifier in this mode using large gain Also can cutoff device by reverse biasing both junctions Can also drive into saturation by forward biasing junctions Can create switch by driving device from cutoff (OFF) to saturation (ON) Inverted mode with junctions reversed from active mode is not commonlyoptimized to achieve high level of performance and is seldom usedElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsAmplification in bipolar common emitter circuit configuration (left) caused by(1) hole recombination in base, (2) holes injected from emitter into the collector,(3) reverse saturation current at collector junction, (4) base current, and(5) electrons injected into emitter (right).Electronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsElectron and hole distribution generated across a bipolar transistor (left) andmore realistic representation of hole distribution in the base (right).Electronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsFour biasing modes of a bipolar device (upper left), regions of bipolar outputcharacteristics associated with biasing modes (lower left), hole distribution atsaturation when VCB 0 (upper right), and hole distribution caused byoversaturation when VCB becomes positive (lower right).Electronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBiasing circuit used to switch bipolar device in common emitter configuration (left)and resultant output characteristics showing response of this device as it variesfrom cutoff (C) through saturation (S) (right).Electronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction Transistors Early effect caused by base narrowing at increasing reverse bias Increases IC at increasing VCE as base narrowsCauses upward slope of IC-VCE characteristic in active regionSlope increases at increasing IB because of higher IC caused by current gainCauses slope to intersect voltage axis at Early voltage VAElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBase narrowing of p-n-p transistor (left) causing increase in collector current in thecommon emitter configuration (right). Output characteristics can be roughlyextrapolated to an intersection at the voltage axis at the Early voltage VA.Electronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction Transistors BJT will also suffer avalanche breakdown at high voltage Common base configuration with IE 0 will undergo avalanche breakdownat BVCBO near breakdown voltage of collector-base junction Common emitter with IB 0 will undergo breakdown at even lower voltage Caused by carriers with the same carrier type as the base being swept backinto the base after impact ionization in the collector junction Causes increase in emitter current to compensate increased charge in base Higher emitter current causes even more avalanche multiplication atcollector junction lowering BVCEO for common emitter compared to BVCBOElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsAvalanche breakdown occurring at BVCBO in common base configuration at IE 0(left) and at BVCEO in common emitter configuration at IB 0 (right).Electronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction Transistors Will evaluate five different BJT characteristics DC current gain hFE given by IC/IBSmall-signal current gain hfe given by ΔIC/ΔIBOutput conductance hoe given by ΔIC/ΔVCEEarly effect as represented by the Early voltage VABreakdown voltage given by BVCEOElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsRelevant Measurements:1)2)3)4)hFE IC/IB (DC Current Gain at VCE)hfe Δ IC/ Δ IB (AC Current Gain at VCE)hoe Δ IC/ Δ VCE (Conductance at IB)Create Tables for Various ParametersPin configuration for 2N4400 NPN transistor(upper left), NPN transistor symbol (upperright), and common emitter test circuit (bottom)DC Current IC and current gain hFE measured at different IB versus VCEElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBipolar IC – VCE Test CurvesElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBipolar IC – VCE DC CharacteristicsElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsDC current gain hFE calculated at increasing IB versus VCE (left) andoutput conductance hoe measured between two voltages calculatedat increasing VCE versus IB (right).Electronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBipolar Early Voltage Test CurvesElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBipolar IC – VCE DC Characteristics Used to Extract Early VoltageElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBipolar Common Emitter Breakdown CharacteristicsElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Bipolar Junction TransistorsBipolar Breakdown Characteristics Used toDetermine Breakdown Voltage BVCEOElectronic Devices Laboratorymtinker@utdallas.eduCE/EE 3110
Electronic Devices Laboratory mtinker@utdallas.edu CE/EE 3110 Amplification in bipolar common emitter circuit configuration (left) caused by (1) hole recombination in base, (2) holes injected from emitter into the collector,
A bipolar (junction) transistor (BJT) is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their
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The basic Bipolar transistor or BJT is two diodes constructed back to back on a piece of silicon. (Another kind of transistor is the Junction Field Effect Transistor of JFET. The theory and labeling of the terminals is a little different for the JF
Bipolar Junction Transistors (BJT) PNP & NPN (Emitter Base Collector) Note: NPN’s are more commonly encountered due to greater ease of production. Bipolar (majority and minority carriers) Forward voltage characteristics of PN junction (approximately 0
1. Active Region - the transistor operates as an amplifier and . Ic β.Ib 2. Saturation -the transistor is "fully ON" operating as a switch and . Ic I(saturation) 3. Cut-off -the transistor is "fullyOFF" operating as a switch and . Ic 0. Typical Bipolar Tran
other types, such as triac, gate turn -off thyristor (GTO's), bipolar power transistor (BJT's), power MOS field-effect transistor (MOSFET's), insulated gate bipolar transistor (IGBT's), static induction transistor (SIT's) and MOS-controlled thyristor (MCT's) were introduce. In parallel with the new device evolution, the power rating
The abbreviation BJT, from bipolar junction transistor is often applied to this three-terminal device. The term bipolar reflects the fact that holes and electrons participate in the injection process into the oppositely polarized material.
