Practical Applications Relay Driver - Hacettepe
ContentsDC Biasing of BJTsDC Biasing of BJTsThree States of OperationBJT DC AnalysisDC Biasing CircuitsFixed-Bias CircuitEmitter-Stabilized Bias CircuitVoltage Divider Bias CircuitDC Bias with Voltage FeedbackVarious Di erent Bias Circuitspnp TransistorsBias StabilizationStability FactorsStability of Transistor Circuits with Active ComponentsPractical ApplicationsRelay DriverTransistor SwitchTransistor Switching NetworksLogic GatesCurrent MirrorVoltage Level IndicatorDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-20171 / 59DC Biasing of BJTsDC BiasingBiasing refers to the DC voltages applied to the transistor to put it into active mode, sothat 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.,Point B in the gure below.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-20172 / 59
DC Biasing of BJTsThree States of OperationThree States of OperationProper DC biasing sets the BJT transistor into the active state, so that it can amplifythe AC signal. Let us remember the states of the transistor:IActive: Operating state of the ampli er: IC βIB .Base-Emitter (BE ) junction: forward-biased (ON).Base-Collector (BC ) junction: reverse-biased (OFF).ICut-O : The ampli er is basically o . There is no current, i.e., ICBase-Emitter (BE ) junction: reverse-biased (OFF).Base-Collector (BC ) junction: reverse-biased (OFF).ISaturation: The ampli er is saturated. Voltages are xed, e.g., VCE VCE(sat) 0 V.Output is distorted, i.e., not the same shape as the input waveform.Base-Emitter (BE ) junction: forward-biased (ON).Base-Collector (BC ) junction: forward-biased (ON).Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs IB IE 0 A.15-Mar-20173 / 59BJT DC AnalysisBJT DC Analysis1. Draw the DC equivalent circuit (signal frequency is zero, i.e., f 0)a) Capacitors are open circuit, i.e., XC .b) Kill the AC power sources (short-circuit AC voltage sources and open-circuit ACcurrent sources).c) Inductors are short circuit or replaced by their DC resistance (winding resistance) ifgiven, i.e., XL 0.2. Write KVL for the loop which contains BE junctiona) Take VBE VBE(ON ) to ensure the transistor is ON (or not in the cut-o state).Note: For a pnp transistor, VEB VBE(ON ) .b) Determine the base current IBQ (or emitter current IEQ ).3. Write KVL for the loop which contains CE terminalsa) Assume the transistor is in the active state and take ICQ βIBQ (or ICQ αIEQ ).b) Calculate VCEQ .c) If VCEQ VCE(sat) then the transistor is in the saturation (SAT) state (i.e., ICQ 6 βIBQ ), so take VCEQ VCE(sat) and recalculate ICQ .NOTE: Normally, a BJT should not be in the saturation state if it is used as anampli er.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-20174 / 59
DC Biasing of BJTsDC Biasing CircuitsDC Biasing CircuitsMost common four common-emitter biasing circuits are given below1. Fixed-Bias Circuit2. Emitter-Stabilized Bias Circuit3. Voltage Divider Bias Circuit4. DC Bias with Voltage FeedbackDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-20175 / 59DC Biasing CircuitsFixed-Bias CircuitFixed-bias circuit is given belowLet us start DC analysis by drawing the DC equivalent circuit as shown belowDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-20176 / 59
DC Biasing of BJTsDC Biasing CircuitsBase-Emitter LoopLet us continue with the BE loop shown belowWriting KVL on the BE loopVCC IB RB VBE 0and given VBE VBE(ON ) , we obtain IBQ asIBQ Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)VCC VBE(ON )RBELE230 Electronics IDC Biasing of BJTs15-Mar-20177 / 5915-Mar-20178 / 59DC Biasing CircuitsCollector-Emitter LoopLet us continue with the CE loop shown belowWriting KVL on the CE loop (i.e., DC load-line equation)VCC IC RC VCE 0and given (assuming BJT is in active state)ICQ βIBQwe obtain VCEQ asVCEQ VCC ICQ RCDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I
DC Biasing of BJTsDC Biasing CircuitsSaturationThe term saturation is applied to any system where levels have reached their maximumvalues. A saturated sponge is one that cannot hold another drop of water. For atransistor operating in the saturation region, the current is a maximum value for theparticular design.Note that it is in a region where the characteristic curves join and the collector-to-emittervoltage is at or below VCE(sat) . If we approximate the curves of the left gure by thoseappearing in the right gure, then the saturation voltage VCE(sat) is assumed to be 0 V,i.e,VCE(sat) 0VDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-20179 / 59DC Biasing CircuitsFor the xed-bias con guration shown below, the resulting saturation current (i.e.,maximum current) IC(sat) is given byIC(sat) IC(max) Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)VCC VCE(sat)RCELE230 Electronics IVCC RC15-Mar-201710 / 59
DC Biasing of BJTsDC Biasing CircuitsExample 1: For the gure above, calculate all DC currents and voltages.Solution: Let us nd IBQ , ICQ and VCEQ as followsIBQ VCC VBE(ON )RB 12 0.7 47.08 µA,240kICQ βIBQ (50)(47.08µ) 2.35 mA,VCEQ VCC ICQ RC 12 (2.35m)(2.2k) 6.83 V.As VCEQ VCE(sat) 0 V, transistor is in the active state. Let us also prove it byshowing VBCQ VBC(ON ) 0.7 V as followsVBCQ VBQ VCQ VBEQ VCEQ 0.7 6.83 6.13 V 0.7 V.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201711 / 59DC Biasing CircuitsDC Load LineDC load line equation comes from KVL equation in the CE loop (i.e., output loop). Forthe xed-bias circuit, DC load line equation is given byVCE VCC IC RCLet us draw the load line over output characteristics curve as shown below. Theintersection of the load-line with the output characteristics curve (determined by the basecurrent IBQ ) is the operating point, i.e., Q-point.IThe Q-point is the operating point where the value of RB sets the value of IBQ thatcontrols the values of VCEQ and ICQ .Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201712 / 59
DC Biasing of BJTsDC Biasing CircuitsFixed-bias load line equation: VCE VCC IC RCThe load line end points are the SATURATION and CUTOFF points, i.e.,I IC(sat)end point (on the current axis):IC VCC /RCI VCE(cutoff )VCE 0 Vend point (on the voltage axis):VCE VCCIC 0 mADr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201713 / 59DC Biasing CircuitsThe E ect of IB on the Q-PointMovement of the Q-point with increasing level of IB (or decreasing level of RB ) is shownbelow.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201714 / 59
DC Biasing of BJTsDC Biasing CircuitsThe E ect of RC on the Q-PointE ect of an increasing level of RC on the load line (slope decreases with increasing RC )and the Q-point is shown below.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201715 / 59DC Biasing CircuitsThe E ect of VCC on the Q-PointE ect of an decreasing level of VCC on the load line (end points gets smaller withdecreasing VCC ) and the Q-point is shown below.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201716 / 59
DC Biasing of BJTsDC Biasing CircuitsExample 2: For the xed-bias load line above, calculate VCC , RC and RB .Solution: From the gure, IBQ 25 µA. So, let us nd VCC , RC and RB as followsVCC VCE(cutoff ) 20 V,RC RB VCCIC(sat) 20 2 kΩ,10mVCC VBE(ON )Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)IBQ 20 0.7 772 kΩ.25µELE230 Electronics IDC Biasing of BJTs15-Mar-201717 / 59DC Biasing CircuitsEmitter-Stabilized Bias CircuitAdding a resistor to the emitter circuit stabilizes the bias circuit, as shown below.Let us start DC analysis by drawing the DC equivalent circuit as shown belowDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201718 / 59
DC Biasing of BJTsDC Biasing CircuitsBase-Emitter LoopLet us continue with the BE loop shown belowWriting KVL on the BE loopVCC IB RB VBE IE RE 0VCC IB RB VBE(ON ) (β 1)IB RE 0,we obtain IBQ asIBQ Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.). . . as VBE VBE(ON )andIE (β 1)IB in active modeVCC VBE(ON )RB (β 1)REELE230 Electronics IDC Biasing of BJTs15-Mar-201719 / 59DC Biasing CircuitsSimilarly, we can obtain IEQ directly from the gure below, or dividing the denominatorof the IBQ by (β 1)as followsIEQ IVCC VBE(ON )RB REβ 1It is generally better to calculate IEQ directly to reduce the number of calculations,especially when there is an emitter resistor RE is connected.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201720 / 59
DC Biasing of BJTsDC Biasing CircuitsCollector-Emitter LoopLet us continue with the CE loop shown belowLet us write down the KVL equation on the CE loopVCC IC RC VCE IE RE 0in active modeVCC IC (RC RE ) VCE 0. . . DC load line equation As ICQ βIBQ IEQ in active mode, we obtain VCEQ asVCC IC RC VCE IC RE 0. . . as IC αIE IEVCEQ VCC ICQ (RC RE )Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201721 / 59DC Biasing CircuitsDC Load LineDC load line equation comes from KVL equation in the CE loop (i.e., output loop). Forthe emitter-stabilized bias circuit, DC load line equation is given byVCE VCC IC (RC RE )Let us draw the load line over output characteristics curve as shown below.Here, VCE(cutoff ) VCC and IC(sat) is given byVCCRC REthe value of RBIC(sat) IThe Q-point is the operating point wherethat controls the values of VCEQ and ICQ .Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics Iand RE sets the value of IBQ15-Mar-201722 / 59
DC Biasing of BJTsDC Biasing CircuitsImproved Biased StabilityStability refers to a condition in which the currents and voltages remain fairly constantover a wide range of temperatures and transistor beta (β ) values.IAdding RE resistor to the emitter improves the stability of a transistor.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201723 / 59DC Biasing CircuitsExample 3: For the gure above, calculate all DC currents and voltages.Solution: Let us nd IBQ , ICQ and VCEQ as followsIBQ VCC VBE(ON )RB (β 1)RE 20 0.7 40.13 µA,430k (50 1)(1k)ICQ βIBQ (50)(40.13µ) 2.01 mA,VCEQ VCC ICQ (RC RE ) 20 (2.01m)(2k 1k) 13.97 V.As VCEQ 0 V (VCE(sat) ), transistor is in the active state.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201724 / 59
DC Biasing of BJTsDC Biasing CircuitsVoltage Divider Bias CircuitVoltage divider bias circuit is given belowLet us start DC analysis by drawing the DC equivalent circuit as shown belowDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201725 / 59DC Biasing CircuitsBase-Emitter Loop (Exact Analysis)Let us transform the BE loop circuit shown on the left below to the Thévenin simpli edcircuit on the right belowwhere the Thévenin voltage VBB and Thévenin resistance RBB are calculated as followsR2VCCR1 R2 R1 R2VBB . . . fromthe gure on the left belowRBB. . . fromthe gure on the right belowDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201726 / 59
DC Biasing of BJTsDC Biasing CircuitsWriting KVL on the Thévenin equivalent BE loop shown aboveVBB IB RBB VBE IE RE 0VBB IB RBB VBE(ON ) (β 1)IB RE 0,we obtain IBQ asIBQ . . . as VBE VBE(ON )andIE (β 1)IB in active modeVBB VBE(ON )RBB (β 1)RESimilarly, we obtain IEQ asIEQ Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)VBB VBE(ON )RBB REβ 1ELE230 Electronics IDC Biasing of BJTs15-Mar-201727 / 59DC Biasing CircuitsBase-Emitter Loop (Approximate Analysis)IEQ VBB VBE(ON )RBB /(β 1) REIf we look at the IEQ equation above, we see that if REIEQ where VBB IR2VR1 R2 CCRBBβ 1, equation simpli es toVBB VBE(ON )RE.Approximate approach can be used when (β 1)RE RBB . Approximate analysiscondition can be rewritten as(β 1)RE 10(R1 R2 ).Assuming R1 R2 , we know that (R1 R2 ) R2 . So, the condition above can befurther simpli ed toβRE 10R2 .ISatisfying this condition means that we can safely ignore the base current IB in the DCequivalent circuit and apply the voltage divider rule between R2 and R1 .Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201728 / 59
DC Biasing of BJTsDC Biasing CircuitsCollector-Emitter Loop and DC Load LineIAnalysis on the CE loop (i.e., output loop), is the same as the CE loop analysis of theemitter-stabilized circuit. So, VCEQ is given byVCEQ VCC ICQ (RC RE )where ICQ IEQ .ISimilarly, DC load line analysis is also the same as the DC load line of theemitter-stabilized circuit. So, DC load line equation is given byVCE VCC IC (RC RE )Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201729 / 59DC Biasing CircuitsExample 4: For the gure above, calculate all DC currents and voltages using both exactand approximate analysis.Solution: Let us rst nd the Thévenin voltage VBB and resistance RBB as followsR23.9kVCC 22 2 V,R1 R239k 3.9k R1 R2 3.9k 39k 3.55 kΩ.VBB RBBDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201730 / 59
DC Biasing of BJTsDC Biasing CircuitsNow, let us calculate IBQ , ICQ and VCEQ as followsIEQ ICQVCEQVBB VBE(ON ) 2 0.7 0.85 mA,3.55k/(140 1) 1.5kRBB /(β 1) RE IEQ 0.85 mA, VCC ICQ (RC RE ) 22 (0.85m)(10k 1.5k) 12.23 V.As βRE 10R2 (i.e., 210 kΩ 39 kΩ), we can use the approximate analysis and ignoreIB and RBB as followsIEQ ICQVCEQVBB VBE(ON ) 2 0.7 0.87 mA,1.5kRE IEQ 0.87 mA, VCC ICQ (RC RE ) 22 (0.87m)(10k 1.5k) 12 V.We see that approximate analysis provides close values to the exact analysis. Thedi erences in ICQ and VCEQ are only 0.02 mA and 0.23 V, respectively.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201731 / 59DC Biasing CircuitsDC Bias with Voltage FeedbackAnother way to improve the stability of a bias circuit is to add a feedback path fromcollector to base as shown belowLet us start DC analysis by drawing the DC equivalent circuit as shown belowDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201732 / 59
DC Biasing of BJTsDC Biasing CircuitsBase-Emitter LoopLet us continue with the BE loop shown belowWe can write KVL equation on the BE loop noting that IC0 IC IB IE0VCC ICRC IB RF VBE IE RE 0VCC IE RC IERF VBE(ON ) IE RE 0,β 1and we obtain IEQ asIEQDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.). . . as VBE VBE(ON )VCC VBE(ON ) RF (RC RE )β 1ELE230 Electronics IDC Biasing of BJTsIB IEβ 1andin active mode15-Mar-201733 / 59DC Biasing CircuitsCollector-Emitter LoopLet us continue with the CE loop shown belowLet us write down the KVL equation on the CE loop noting that IC0 IC IB0VCC ICRC VCE IE RE 00and IC in active mode ICVCC IC (RC RE ) VCE 0. . . DC load line equationAs ICQ IEQ in active mode, we obtain VCEQ asVCC IC RC VCE IC RE 0. . . as IC IEVCEQ VCC ICQ (RC RE )Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201734 / 59
DC Biasing of BJTsDC Biasing CircuitsDC Load LineINote that IC0 IE , andIC IEin active mode (and β is high).ISo, DC load line analysis is the same as the DC load line of the emitter-stabilized circuit.So, DC load line equation is given byVCE VCC IC (RC RE )Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201735 / 59DC Biasing CircuitsVarious Di erent Bias CircuitsExample 5: For the gure above, calculate all DC currents and voltages.Solution: Let us nd IEQ , ICQ and VCEQ as followsIEQ 0 VBE(ON ) VEERB /(β 1) RE 20 0.7 4.16 mA,240k/(90 1) 2kICQ IEQ 4.16 mA,VCEQ 0 IEQ RE VEE 20 (4.16m)(2k) 11.68 V.As VCEQ VCE(sat) 0 V, transistor is in the active state.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201736 / 59
DC Biasing of BJTspnpDC Biasing CircuitsTransistorsThe analysis for pnp bias transistor circuits is the same as that for npn transistor circuits.The only di erences are that1. Currents are owing in the opposite direction.2. Voltages have opposite polarity, e.g., VEB VBE(ON ) 0.7 V in the active mode.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201737 / 59DC Biasing CircuitsExample 6: For the gure above, calculate all DC currents and voltages.Solution: As βRE 10R2 , i.e., 132 kΩ 100 kΩ, we can ignore the base current IB anduse the approximate approach. Thus, we can nd VBB , IEQ , ICQ and VCEQ as followsR210kVCC ( 18) 3.16 VR1 R247k 10k0 0.7 ( 3.16)2.460 VEB VB 2.24 mA, RE1.1k1.1k IEQ 2.24 mA,VB IEQICQVECQ 0 ICQ (RC RE ) VCC (2.24m)(2.4k 1.1k) ( 18) 10.16 V.As VECQ VCE(sat) 0 V, transistor is in the active state.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201738 / 59
DC Biasing of BJTsBias StabilizationBias StabilizationVariation of three BJT (Si) parameters (ICO , β and VBE(ON ) ) with temperature aresummarized belowT ICO βICO β VBE(ON ) (reverse saturation current)doubles in value for every 10 C(transistor current gain) increases with increasing temperatureVBE(ON ) (forward bias potential of the base-emitter junction)decreases about 2.5 mV per 1 C increase in temperatureDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201739 / 59Bias StabilizationVariation of the transistor parameters with temperature causes a shift in the operatingpoint (i.e., Q-point).Figures below (at 25 C on the left and at 100 C on the right) show the shift of theQ-point (or DC bias point) due to temperature change for a xed-bias circuit.at 25 CDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics Iat 100 C15-Mar-201740 / 59
DC Biasing of BJTsBias StabilizationStability FactorsStability of the collector current IC depends on the stability of several parameters likeICO , β , VBE(ON ) , VCC , RB , RC , etc.A stability factor S is de ned for each of the parameters a ecting bias stability as follows:SICO Sβ SVBE(ON ) IC IC ICO ICO IC IC β β IC VBE(ON ) β,VBE(ON ) ,.constantICO ,VBE(ON ) ,.constant IC VBE(ON )ICO ,β,.constantWe know that di erential dIC is given by the linear map of parameter di erentials asfollowsdIC I IC IC ICdICO dβ dVBE(ON ) · · · ICO β VBE(ON )Thus, we obtain the collector-current change IC using the stability factors as follows IC SICO ICO Sβ β SVBE(ON ) VBE(ON )Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201741 / 59Bias StabilizationDerivation of Stability Factors (Voltage-DividerBias Circuit)Let us write down the active mode collector current and BE -loop KVL equations for thecircuit shown above,IC βIB (β 1) ICOVBB IB RBB VBE(ON ) (IB IC )RECombining the two equations above, we obtain the expression for IC asIC RBB (β 1) (RBB RE )βVBB VBE(ON ) ICO (β 1) RERBB (β 1) REDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201742 / 59
DC Biasing of BJTsIC RBBBias Stabilization (β 1) (RBB RE )βVBB VBE(ON ) ICO (β 1) RERBB (β 1) RE1. From the IC equation above, let us derive SICO SICO (β 1) IC ICORBB RERBB (β 1) RE2. From the IC equation above, let us derive SVBE(ON ) SVBE(ON ) 3. In order to derive Sβ IC βIC asRBB IC VBE(ON )as β (β 1) RE, let us rst simplify IC equation by letting ICO 0RBB βVBB VBE(ON ) (β 1) REDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201743 / 59Bias StabilizationUsing the simpli ed IC equation we can express IC1 and IC2 as follows β1VBB VBE(ON )RBB (β1 1) RE β2 VBB VBE(ON ) RBB (β2 1) REIC1 IC2Thus, using the equations above, let us obrain the ratioIC2 IC1IC1asIC2 IC1β2 β1RBB RE IC1β1RBB (β2 1) REFrom the equation above, we can obtain the ratio β β2 β1 as IC βby using IC IC2 IC1 andIC 1RBB RE IC ββ1 RBB (β2 1) REThus, as Sβ IC β IC βSβ Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)IC 1RBB REβ1 RBB (β2 1) REELE230 Electronics I15-Mar-201744 / 59
DC Biasing of BJTsBias StabilizationStability Factors for Other Bias CircuitsA. For the xed-bias circuit, i.e., by substituting RE 0 and RBB RB , the stabilityfactors are given bySICO β 1 βRBIC1Sβ β1SVBE(ON ) B. For the emitter-stabilized bias circuit, i.e., RBB RB and RB RE , the stabilityfactors are given bySICO (β 1)RB RE RB (β 1) REβ 1(β 1) RE1 RB βRB (β 1) REIC1IC1RB RE Sβ β1 RB (β2 1) REβ1SVBE(ON ) Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs1(β2 1) RE1 RB15-Mar-201745 / 59Bias StabilizationC. For the voltage-divider bias circuit with (β 1)RE 10RBB , the stability factors aregiven byRBB RE 1 RBB RBB (β 1) RERE β 1 SVBE(ON ) RBB (β 1) RERE IC1IC1RBB RERBB Sβ 1 β1 RBB (β2 1) REβ1 β2RESICO (β 1)D. For the voltage-feedback bias circuit, i.e., RBB RF , replacing RE withRCE RC RE and RF RCE , the stability factors are given bySICO (β 1)RF RCE RF (β 1) RCEβ 1(β 1) RCE1 RF βRF (β 1) RCEIC1IC1RF RCE Sβ β1 RF (β2 1) RCEβ1SVBE(ON ) Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I1(β2 1) RCE1 RF15-Mar-201746 / 59
DC Biasing of BJTsBias StabilizationTemperatureICOβ 65 C0.02 nA200.85 V25 C0.1 nA500.65 V100 C20 nA800.48 V175 C3.3 µA1200.30 VVBE(ON )Example 7: Find and compare the collector current change IC when the temperaturerises from 25 C to 100 C for the transistor de ned by the table above for the followingbias arrangements.a. Fixed-bias with RB 240 kΩ and IC1 2 mA,b. Voltage-divider bias with RE 4.7 kΩ, RBB /RE 2 and IC1 2 mA.Solution: From the table above, let us rst calculate ICO , β and VBE(ON ) ICO ICO2 ICO1 20n 0.1n 19.9 nA β β2 β1 80 50 30 VBE(ON ) VBE(ON )2 VBE(ON )1 0.48 0.65 0.17 VWe are goiung to calculate IC using IC SICO ICO Sβ β SVBE(ON ) VBE(ON )Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201747 / 59Bias Stabilizationa. Let us calculate the stability factors for the xed-bias circuitSICO β 1 51IC12m 0.04 mAβ150 β 50 0.21 mΩ 1RB240kSβ SVBE(ON )Thus, IC is given by IC (51)(19.9n) (0.04m)(30) ( 0.21m)( 0.17) 1.02µ 1.2m 0.036m 1.236 mAThat means, for the xed-bias circuit IC increases to 3.236 mA at 100 C from 2 mA.b. Let us calculate the stability factors for the voltage-divider bias circuitRBBSICO 1 2 3 1 RE IR2mCBB1Sβ 1 (1 2) 1.5 µA β1 β2RE(50)(80) 1 1SVBE(ON ) 0.21 mΩ 1RE4.7kDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201748 / 59
DC Biasing of BJTsBias StabilizationThus, IC is given by IC (3)(19.9n) (1.5µ)(30) ( 0.21m)( 0.17) 0.060µ 0.045m 0.036m 0.081 mAThat means, for the voltage-divider bias circuit IC increases to 2.08 mA at 100 C from2 mA. Most of the improvement comes from the reduction in Sβ .IThese two results show that voltage-divider bias circuit is much more stable than thexed-bias circuit. In other words, adding RE resistor to the emitter leg of the transistorstabilizes the bias circuit.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201749 / 59Bias StabilizationStability of Transistor Circuits with ActiveComponentsVBE compensationby using a reverse-biased diode at the emitterDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201750 / 59
DC Biasing of BJTsICO ICBias Stabilizationcompensationby replacing R2 with a reverse-biased diodecompensation (without RE ) by using a current mirrorDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201751 / 5915-Mar-201752 / 59Practical ApplicationsPractical ApplicationsRelay DriverTransistor SwitchTransistor Switching NetworksLogic GatesCurrent MirrorVoltage Level IndicatorDr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I
DC Biasing of BJTsPractical ApplicationsRelay DriverWhen the transistor turns OFF, a high voltage (given by vL L (diL /dt)) is inducedacross the coil as shown above. If its magnitude exceeds the maximum ratings of thetransistor, then the semiconductor device will be permanently damaged.This destructive action can be subdued by placing a diode across the coil as shown below.Now, when the transistor turns o , the voltage across the coil will reverse and willforward-bias the diode, placing the diode in its ON state (hence protecting the transistor).Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201753 / 59Practical ApplicationsTransistor SwitchA transistor can be used as a switch to control the ON and OFF states of the light-bulb inthe collector branch of the circuit as shown below.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201754 / 59
DC Biasing of BJTsPractical ApplicationsTransistor Switching NetworksTransistors can also be used as switches for computer and control applications. Thecircuit shown above can be employed an inverter in computer logic circuitry.Inversion process requires that the Q-point switch from cuto (Vo VCE(cutoff ) 5 V)to saturation (Vo VCE(sat) 0 V) along the load line depicted below.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201755 / 59Practical ApplicationsThe total time required for the transistor to switch from the OFF to the ON state isdesignated as ton , and he total time required for a transistor to switch from the ON tothe OFF state is referred to as toff as shown below. ton and toff are de ned byton tr tdtoff ts tf10% to 90% of the output, tdwhere tr is the rise time fromis the delay time between thechanging state of the input and the beginning of a response at the output, ts is thestorage time and and tf the fall time from 90% to 10% of the output.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201756 / 59
DC Biasing of BJTsPractical ApplicationsLogic GatesThe gure above shows a BJT logic OR gate, and similarly The gure below shows a BJTlogic AND gate.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics IDC Biasing of BJTs15-Mar-201757 / 59Practical ApplicationsCurrent MirrorThe current mirror shown below is a DC circuit in which the current through a load iscontrolled by a current at another point in the circuit. That is, the current through theload is indepedent of the load.Homework 1: For the gure above, show that the load current is equal to the loadcontrol current and given byIL Icontrol VCC VBE(ON )Rwhere the transistors are identical (Q1 Q2 ), i.e., VBE1 (ON ) VBE2 (ON ) VBE(ON )and β1 β2 β , and current gain β is high, e.g., β 100.Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201758 / 59
DC Biasing of BJTsPractical ApplicationsVoltage Level IndicatorThe voltage level indicator circuit uses a green LED to indicate when the source voltage isclose to its monitoring level of 9 V. The potentiometer is set to establish 5.4 V at thepoint indicated below. The result is su cient voltage to turn on both the 4.7 V Zener andthe transistor and establish a collector current through the LED su cient in magnitude toturn on the green LED. The LED will immediately turn o , revealing that the supplyvoltage has dropped below 9 V or that the power source has been disconnected (i.e., whenthe voltage set up by the voltage divider circuit drops below 5.4 V).Dr. U. Sezen & Dr. D. Gökçen (Hacettepe Uni.)ELE230 Electronics I15-Mar-201759 / 59
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.,
Nissan Micra - OWM 4734 Nissan Micra - OWM 4734 CPU E6 H33750 1 Battery 2 Ignition switch 3 Fusible link holder 4 Fuse box 5 Fuse and relay box a) accessory relay b) blower motor relay 6 Intelligent power distribution module a) starter relay b) cooling fan hi relay c) cooling fan lo relay d) fuel pump relay e) ignition relay f) ECM relay
38 - Check voltage output to fuel pump @ relay set 39 - Check voltage input to relay set from ignition switch 40 - Check voltage input to fuel pump relay of relay set 41 - Check input voltage to control relay of relay set 42 - Check input voltage to control relay of relay set (continued)
Power MOSFET Relay Specifications (G6D Relay) The following specifications apply to G6D Relays mounted in a G70D Relay Terminal and not the G6D Relay itself. Coil Ratings (per G6D Relay) Note: 1. The must-operate voltage is 75% or less of the rated voltage if the relay is mounted upside down. 2. Rated current and coil resistance were measured .
Results are provided for actual relay testing. Part I: Distance Relay Tests (Texas A&M University) Distance relay testing can evaluate relay performance, calibrate relay settings, and identify system conditions that could cause unexpected relay operation. Developing a relay testing methodology requires consideration of how to model the power .
Install Your Relay Switch Do not use this sensor in hazardous (classified) locations or life safety applications. Step 1: Mount your Relay Switch. Mount your Relay Switch with screws through the flange holes, secure it with Velcro or simply place it on a flat surface. Step 2: Connect your Relay Switch to AVTECH's Light Tower & Relay Adapter .
Relay data and relay setting management Management of relay versions and models World‘s largest library with relay setting data models Library expandable by customer & via relay setting model generator Result import from different test device software: Omicron, Doble, Programma, etc.
Relay AE RLY-538 5 v 178 ohm Resistor DPDT 270 ohms ½ watt Control Tortoise with 5 volt Relay-12 volts DC 12 volts DC Relay On Off To Tortoise Relay “stick” contacts “On” Button powers relay, “stick” contact holds it on “Off” button bypasses relay coil so it drops out Can have any no. of
Relay Computer Harry Porter, Ph.D. Portland State University April 24, 2006. 2. 3 V. 4 Double Throw Relay. 5 V Double Throw Relay. 6 Four Pole, Double Throw Relay. 7 V Four Pole, Double Throw Relay. 8. 9 Schematic Diagrams. 10 Schematic Diagrams Assume other terminal is connected to ground. 11 Schematic Diagrams
