Building Blocks of Integrated-Circuit Amplifiers C H A P T E R 7 Building Blocks of Integrated-Circuit Amplifiers Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.1 The basic gain cells of IC amplifiers: (a) current-source- or active-loaded common-source amplifier; (b) current-source- or active-loaded common-emitter amplifier; (c) small-signal equivalent circuit of (a); and (d) small-signal equivalent circuit of (b). 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 7.3 (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.

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 7.8 Determining the output resistance of the MOS cascode amplifier. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.9 (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 7.10 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 7.11 A cascode amplifier with a cascode current-source load. 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 7.14 The output resistance expression of the cascode can be used to find the output resistance of a source-degenerated common-source 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 7.15 Double cascoding. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.16 The folded cascode. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.17 (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 7.18 Determining the output resistant Ro of the BJT cascode amplifier. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.19 A BJT cascode amplifier with a cascode current source. 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 7.21 BiCMOS cascodes. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7. 22 Circuit for a basic MOSFET constant-current source Figure 7.22 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 7.23 Basic MOSFET current mirror. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7. 24 Output characteristic of the current source in Fig. 7 Figure 7.24 Output characteristic of the current source in Fig. 7.22 and the current mirror of Fig. 7.23 for the case of Q2 matched to Q1. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.25 A current-steering circuit. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.26 Application of the constant currents I2 and I5 generated in the current-steering circuit of Fig. 7.25. 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 7.27 (a) A current source; and (b) a current sink. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.28 The basic BJT current mirror. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.29 Analysis of the current mirror taking into account the finite  of the BJTs. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.30 A simple BJT current source. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.31 Generation of a number of constant currents of various magnitudes. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure E7.19 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.32 A cascode MOS current mirror. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.33 A current mirror with base-current compensation. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.34 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 7.35 The Wilson MOS mirror: (a) circuit; (b) analysis to determine output resistance; (c) modified circuit. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.36 The Widlar current source. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.37 Circuits for Example 7.6. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.38 (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.

Figure 7.39 Circuit for Example 7.7. 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 7. 41 (a) A CC–CB amplifier Figure 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.

Figure 7.42 Circuits for Example 7.8. (continued on following page) Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Table 7.A.3 Comparison of the MOSFET and the BJT Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Table 7.A.3 (cont.) 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 7.A.2 Frequency response of a CS amplifier loaded with a capacitance CL and fed with an ideal voltage source. It is assumed that the transistor is operating at frequencies much lower than fT, and thus the internal capacitances are not taken into account. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure 7.A.3 Increasing ID or W/L increases the bandwidth of a MOSFET amplifier operated at a constant VOV and loaded by a constant capacitance CL. Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.12 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.13 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.18 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.19 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.28 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.29 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.31 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

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Figure P7.37 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

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Figure P7.44 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

Figure P7.45 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

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Figure P7.62 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.

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Figure P7.107 Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc.