* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Document
Survey
Document related concepts
Electronic engineering wikipedia , lookup
Ground loop (electricity) wikipedia , lookup
Dynamic range compression wikipedia , lookup
Semiconductor device wikipedia , lookup
Integrated circuit wikipedia , lookup
Two-port network wikipedia , lookup
Regenerative circuit wikipedia , lookup
Flexible electronics wikipedia , lookup
Oscilloscope history wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Transcript
A.1 Large Signal Operation-Transfer Charact. Figure 6.32 Biasing the BJT amplifier at a point Q located on the active-mode segment of the VTC. Microelectronic Circuits, Sixth Edition 1 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. A.1 Large Signal Operation-Transfer Charact. O CE VCC RC iC iC I S e BE / VT I S e I / VT I / VT O VCC RC I S e ICsat VCC VCEsat RC 2 A.2 Amplifier Gain BJT is biased at a point in active region called Quiescent point I C I S e BE / VT (5.53) VCE VCC RC IC (5.54) d O A d I I VBE 1 A I S e VBE / VT RC VT IC RC VRC A VT VT (5.56) VRC VCC VCE (5.57) 3 A.3 Graphical Analysis VCC 1 iC CE RC RC CE VCC iC RC 4 A.3 Graphical Analysis IB must be defined previously. Q is quiescent bias point 5 Microelectronic Circuits, Sixth Edition 6 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. A.3 Graphical Analysis Small signal analysis around the bias Q point 7 A.3 Operation as a Switch iB I VBE RB iC iB C VCC RC iC IC (EOS) I B (EOS) VCC 0.3 RC IC (EOS) VI (EOS) I B (EOS) RB VBE Utilize the cutoff and saturation modes. ICsat Edge of saturation (EOS) 8 VCC VCEsat RC A.4 Small Signal Operation and Models DC bias conditions are set by these equations. I E IC / I C I S e VBE / VT I B IC / VC VCE VCC IC RC 9 A.4.1 collector current and transconductance BE VBE be iC I S e BE / VT I S e (VBE be )/ VT I S e be / VT iC IC e iC VBE / VT e be / VT be IC 1 for small be VT IC iC IC be VT Small signal approximation Small signal component IC ic be VT or ic gm be where gm is called transconductance ! 10 IC gm VT or iC gm BE iC IC A.4.1 collector current and transconductance Small signal approximation is restricted to an almost linear segment of i-v curve. 11 A.4.2 base current and input resistance at base iC IC 1 IC iB be VT 1 IC ib be VT iB I B ib r be ib Therefore, or ib gm Small signal r is defined for small signal ib r gm VT r IB or is called small signal base resistance 12 be A.4.3 emitter current and input resistance iE iC IC iC i E I E ie iC IC IE ie be be VT VT re be ie Therefore, For small signal vbe Small signal reis defined for small signal ie VT re IE r and re relationship is called small signal emitter resistance re gm 13 1 gm r ( 1)re Figure 6.38 Illustrating the definition of rπ and re. Microelectronic Circuits, Sixth Edition 14 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.39 The amplifier circuit of Fig. 6.36(a) with the dc sources (VBE and VCC) eliminated (short-circuited). Thus only the signal components are present. Note that this is a representation of the signal operation of the BJT and not an actual amplifier circuit. Microelectronic Circuits, Sixth Edition 15 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. A.4.4 Voltage Gain C VCC iC RC VCC ( IC ic ) RC (VCC IC RC ) ic RC VC ic RC c ic RC gm be RC ( gm RC ) be Voltage gain of amplifier is c A gm RC be or IC RC A VT Voltage gain is directly proportional to collector current Ic. 16 A.4.5 Separating Signal and DC quantities • Voltage and current are composed of DC and signal components. • since ideal dc supply voltage does not change, the signal voltage across it will be zero. Amplifier circuit with DC sources Eliminated (short circuited) => We will make equivalent small signal circuit using equivalent small signal transistor model 17 A.4.6 The Hybrid- Model • the equivalent small signal circuit model ie be r be r gm be be r (1 ) be (1 gm r ) r 1 be / re 18 gm be gm ( ib r ) ( gm r )ib ib A.4.7 The T Model ib be re be re be gm be (1 ) be ( 1)re re be (1 gm re ) 1 re 1 be r 19 gm be gm ( ie re ) ( gm re )ie ie A.4.8 Application of small signal equivalent circuits 1. Determine DC operating point of BJT (particularly Ic) 2. Calculate values of small signal model parameters such as gm = Ic/VT, r = /gm, and re = VT/IE. 3. eliminate DC sources by replacing DC voltage with short circuit and DC current with open circuit. 4. Replace BJT with one of small signal equivalent circuit models. 5. Analyze the resulting circuit ! 20 A.4.8 Application of small signal equivalent circuits DC operating point VBB VBE IB 0.023 mA RBB IC I B 2.3 mA VC VCC iC RC 3.1 V Small signal model parameters - model used ! VT re 10.8 IE gm r 21 IC 92 mA/V VT gm 1.09 A.4.8 Application of small signal equivalent circuits r be i r RBB 1.09 i 0.011 i 101.09 (5.105) o gm be RC 92 0.011 i 3 3.04 i o A 3.04 V/V i (5.106) 22 A.4.8 Application of small signal equivalent circuits DC operating point IE 10 VE 0.93 mA RE IC 0.92 mA VC 10 IC RC 5.4 V Small signal model parameters 0.99 re VT 25 mV 27 I E 0.93 mA o A 183.3 V/V i 23 A.4.10 Small signal model to account for Early effect. Early effect VA +VCE ro IC VA IC o gmbe ( RC // ro ) In most cases, since ro >> RC, reduction in gain is not critical. Furthermore, we can neglect ro in our analysis for simplifying the circuit analysis. 24 A.4.10 Small signal model to account for Early effect. 25 A.5 Single Stage BJT Amplifier 26 A.5 Single Stage BJT Amplifier Table 5.5 27 A.5.1 The common emitter (CE) amplifier - AC ground at emitter - CE is bypass capacitor - CC1 is coupling capacitor Rin i ii RB Rib Rib r Rin Small signal model for circuit 28 r A.5.2 CE Amplifier with emitter resistance Small signal model for circuit Rin RB Rib Rib i b ie i re Re and ie ib (1 )ie 1 Rib ( 1)(re Re ) - It says that input resistance looking into base is +1 times total resistance in emitter (resistance reflection rule) 29 A.5.2 CE Amplifier with emitter resistance Rib (with Re included) ( 1)( re Re ) Re 1 1 gm Re Rib (without Re ) ( 1)re re - Inclusion of RE in emitter can substantially increase the input resistance. - Therefore, designer can control Rin by controlling value of RE. Now we determine the voltage gain o ic ( RC RL ) ie ( RC RL ) ( RC RL ) A re Re o ( RC RL ) A i re Re ~1 A o and RC re Re - voltage gain from base to collector is equal to ratio of collector resistance to emitter resistance. 30 A.5.2 CE Amplifier with emitter resistance Avo can be expressed in other form. RC A o re 1 Re / re gm RC gm RC A o 1 Re / re 1 gm Re There is trade between increase in input resistance and decrease in voltage gain by factor of 1+gmRe Output resistance : ios ie Ais and ( RB Rib ) re Re Rout RC ii i / Rin if RB >> Rib Rib=(+1)(re+Re) 31 Rin ie Ais i ( 1)(re Re ) Ais re Re A.5.2 CE Amplifier with emitter resistance Summary of CE amplifier with emitter resistance - Input resistance is increased by factor of 1+gmRe. - The voltage gain from base to collector is reduced by factor of 1+gmRe. - For the same nonlinear distortion, input signal can be increased by factor of 1+gmRe. - The overall voltage gain is less dependant on . - The high frequency response is significantly improved. 32 A.5.3 The Common Base (CB) Amplifier Small signal model for circuit Rin re ie i re and o ie ( RC RL ) o A ( RC RL ) gm ( RC RL ) i re 33 A.5.3 The Common Base (CB) Amplifier Summary of CB amplifier with emitter resistance - Input resistance is very low (re). - Short circuit current gain is nearly unity (). - Like CE amplifier, it has high output resistance RC. - A very importance application of CB amplifier is current buffer. 34 A.5.4 The Common Collector (CC) Amplifier CC amplifier is commonly used and known by name of emitter follower. Redrawn for rO parallel with RL. Unlike CE and CB, CC amp. is not unilateral because Rin depends on output RL ! 35 Microelectronic Circuits, Sixth Edition 36 Sedra/Smith Copyright © 2010 by Figure 5.2 The enhancement-type NMOS transistor with a positive voltage applied to the gate. An n channel is induced at the top of the substrate beneath the gate. Microelectronic Circuits, Sixth Edition 37 Sedra/Smith Copyright © 2010 by Microelectronic Circuits, Sixth Edition 38 Sedra/Smith Copyright © 2010 by Microelectronic Circuits, Sixth Edition 39 Sedra/Smith Copyright © 2010 by Microelectronic Circuits, Sixth Edition 40 Sedra/Smith Copyright © 2010 by Microelectronic Circuits, Sixth Edition 41 Sedra/Smith Copyright © 2010 by Microelectronic Circuits, Sixth Edition 42 Sedra/Smith Copyright © 2010 by Microelectronic Circuits, Sixth Edition 43 Sedra/Smith Copyright © 2010 by Microelectronic Circuits, Sixth Edition 44 Sedra/Smith Copyright © 2010 by Figure 5.10 Cross-section of a CMOS integrated circuit. Note that the PMOS transistor is formed in a separate n-type region, known as an n well. Another arrangement is also possible in which an n-type body is used and the n device is formed in a p well. Not shown are the connections made to the p-type body and to the n well; the latter functions as the body terminal for the p-channel device. Microelectronic Circuits, Sixth Edition 45 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition 46 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition 47 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition 48 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 5.20 The relative levels of the terminal voltages of the enhancement-type PMOS transistor for operation in the triode region and in the saturation region. Microelectronic Circuits, Sixth Edition 49 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition 50 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 5.28 Biasing the MOSFET amplifier at a point Q located on the segment AB of the VTC. Microelectronic Circuits, Sixth Edition 51 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition 52 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition 53 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 5.31 Graphical construction to determine the voltage transfer characteristic of the amplifier in Fig. 5.29(a). Microelectronic Circuits, Sixth Edition 54 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 5.33 Two load lines and corresponding bias points. Bias point Q1 does not leave sufficient room for positive signal swing at the drain (too close to VDD). Bias point Q2 is too close to the boundary of the triode region and might not allow for sufficient negative signal swing. Microelectronic Circuits, Sixth Edition 55 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 5.43 The three basic MOSFET amplifier configurations. Microelectronic Circuits, Sixth Edition 56 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition 57 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 5.49 Illustrating the need for a unity-gain buffer amplifier. Microelectronic Circuits, Sixth Edition 58 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 5.57 (a) Common-source amplifier based on the circuit of Fig. 5.56. (b) Equivalent circuit of the amplifier for small-signal analysis. Microelectronic Circuits, Sixth Edition 59 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.