CHAPTER 6 Building Blocks of Integrated-Circuit Amplifiers Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.1 The basic gain cells of IC amplifiers: (a) current-source- or active-loaded common-source amplifier; (b) current-source- or activeloaded common common-emitter emitter amplifier; (c) small small-signal signal equivalent circuit of (a); and (d) small small-signal signal equivalent circuit of (b). (b) Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. 6 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.3 (a) The CS amplifier with the current-source load implemented with a p-channel MOSFET Q2 ; (b) the circuit with Q2 replaced with its large-signal model; and (c) small-signal equivalent circuit of the amplifier. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. 6 Microelectronic Circuits, Sixth Edition 6 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. 6 6 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.8 Determining the output resistance of the MOS cascode amplifier. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.9 (a) A MOS cascode amplifier with an ideal current-source load; (b) equivalent circuit representation of the cascode output. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.10 Employing a cascode transistor Q3 to raise the output resistance of the current source Q4. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.11 A cascode amplifier with a cascode current-source load. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. 6 Microelectronic Circuits, Sixth Edition 6 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.14 The output resistance expression of the cascode can be used to find the output resistance of a source-degenerated commonsource amplifier. Here, a useful interpretation of the result is that Rs increases the output resistance by the factor (1 + gmRs). Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.15 Double cascoding. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.16 The folded cascode. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.17 (a) A BJT cascode amplifier with an ideal current-source load; (b) small-signal equivalent-circuit representation of the output of the cascode amplifier; (c) the cascode amplifier with the output short-circuited to ground, and (d) equivalent circuit representation of (c). Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.18 Determining the output resistant Ro of the BJT cascode amplifier. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.19 6 19 A BJT cascode amplifier with a cascode current source source. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. 6 Microelectronic Circuits, Sixth Edition Figure 6.21 BiCMOS cascodes. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.22 Circuit for a basic MOSFET constant-current source. For proper operation, the output terminal, that is, the drain of Q2, must be connected to a circuit that ensures that Q2 operates in saturation. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.23 6 23 Basic MOSFET current mirror. mirror Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.24 Output characteristic of the current source in Fig. 6.22 and the current mirror of Fig. 6.23 for the case of Q2 matched to Q1. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.25 A current-steering circuit. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.26 6 26 Application of the constant currents I2 and I5 generated in the current-steering current steering circuit of Fig Fig. 6 6.25. 25 Constant-current Constant current I2 is the bias current for the source follower Q6, and constant-current I5 is the load current for the common-source amplier Q7. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.27 (a) A current source; and (b) a current sink. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.28 The basic BJT current mirror. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.29 6 29 Analysis of the current mirror taking into account the finite β of the BJTs. BJTs Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.30 6 30 A simple BJT current source. source Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.31 6 31 Generation of a number of constant currents of various magnitudes magnitudes. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.32 6 32 A cascode MOS current mirror mirror. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.33 A current mirror with base-current compensation. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.34 The Wilson bipolar current mirror: (a) circuit showing analysis to determine the current transfer ratio; (b) determining the output resistance. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.35 6 35 The Wilson MOS mirror: (a) circuit; (b) analysis to determine output resistance; (c) modified circuit. circuit Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.36 The Widlar current source. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6.38 (a) CC–CE amplifier; (b) CD–CS amplifier; (c) CD–CE amplifier.01 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. 6 Figure 7.40 (a) The Darlington configuration; (b) voltage follower using the Darlington configuration; (c) the Darlington follower with a bias current I supplied to Q1 to ensure that its β remains high. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. Figure 6 7.41 (a) A CC–CB amplifier. (b) Another version of the CC–CB circuit with Q2 implemented using a pnp transistor. (c) The MOSFET version of the circuit in (a). Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.
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