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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
A.1 Large Signal Operation-Transfer Charact. sedr42021_0526a.jpg
A.2 Amplifier Gain BJT is biased at a point in active region called Quiescent point
A.3 Graphical Analysis sedr42021_0527.jpg
A.3 Graphical Analysis IB must be defined previously. Q is quiescent bias point sedr42021_0529.jpg
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
A.3 Graphical Analysis Small signal analysis around the bias Q point sedr42021_0530a.jpg
A.3 Operation as a Switch Utilize the cutoff and saturation modes. Edge of saturation (EOS) sedr42021_0532.jpg
A.4 Small Signal Operation and Models DC bias conditions are set by these equations. sedr42021_0548a.jpg
A.4.1 collector current and transconductance Small signal approximation Small signal component or where or gm is called transconductance !
A.4.1 collector current and transconductance sedr42021_0549.jpg Small signal approximation is restricted to an almost linear segment of i-v curve.
A.4.2 base current and input resistance at base or Small signal r is defined for small signal ib Therefore, or is called small signal base resistance
A.4.3 emitter current and input resistance For small signal vbe Small signal reis defined for small signal ie Therefore, is called small signal emitter resistance r and re relationship
Figure 6.38 Illustrating the definition of rπ and re. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Figure 6. 39 The amplifier circuit of Fig. 6 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
A.4.4 Voltage Gain Voltage gain of amplifier is or Voltage gain is directly proportional to collector current Ic.
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 sedr42021_0550.jpg
A.4.6 The Hybrid- Model the equivalent small signal circuit model sedr42021_0551a.jpg
A.4.7 The T Model sedr42021_0552a.jpg
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 ! sedr42021_0551a.jpg
A.4.8 Application of small signal equivalent circuits DC operating point Small signal model parameters - model used ! sedr42021_0553a.jpg
A.4.8 Application of small signal equivalent circuits
A.4.8 Application of small signal equivalent circuits DC operating point Small signal model parameters sedr42021_0555a.jpg
A.4.10 Small signal model to account for Early effect. 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. sedr42021_0558a.jpg
A.4.10 Small signal model to account for Early effect. sedr42021_tb0504a.jpg
A.5 Single Stage BJT Amplifier
A.5 Single Stage BJT Amplifier sedr42021_tb0505a.jpg Table 5.5
A.5.1 The common emitter (CE) amplifier - AC ground at emitter - CE is bypass capacitor - CC1 is coupling capacitor sedr42021_0560a.jpg Small signal model for circuit
A.5.2 CE Amplifier with emitter resistance Small signal model for circuit and sedr42021_0561a.jpg - It says that input resistance looking into base is +1 times total resistance in emitter (resistance reflection rule)
A.5.2 CE Amplifier with emitter resistance 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 ~ 1 and voltage gain from base to collector is equal to ratio of collector resistance to emitter resistance.
A.5.2 CE Amplifier with emitter resistance Avo can be expressed in other form. There is trade between increase in input resistance and decrease in voltage gain by factor of 1+gmRe Output resistance : and if RB >> Rib Rib=(+1)(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.
A.5.3 The Common Base (CB) Amplifier Small signal model for circuit sedr42021_0562a.jpg and
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.
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. sedr42021_0563a.jpg Unlike CE and CB, CC amp. is not unilateral because Rin depends on output RL !
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Figure 5. 10 Cross-section of a CMOS integrated circuit 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Figure 5. 33 Two load lines and corresponding bias points 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Figure 5.43 The three basic MOSFET amplifier configurations. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
Microelectronic Circuits, Sixth Edition 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 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 Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.