1Signal Generators and Waveform-Shaping Circuits*Microelectronic Circuits - Fifth Edition Sedra/Smith2Copyright 2004 by Oxford University Press, Inc.Figure 13.1 The basic structure of a sinusoidal oscillator. A positive-feedback loop is formed by an amplifier and a frequency-selective network. In an actual oscillator circuit, no input signal will be present; here an input signal xs is employed to help explain the principle of operation.*Microelectronic Circuits - Fifth Edition Sedra/Smith3Copyright 2004 by Oxford University Press, Inc.Figure 13.2 Dependence of the oscillator-frequency stability on the slope of the phase response. A steep phase response (i.e., large df/dw) results in a samll Dw0 for a given change in phase Df (resulting from a change (due, for example, to temperature) in a circuit component).*Microelectronic Circuits - Fifth Edition Sedra/Smith4Copyright 2004 by Oxford University Press, Inc.Figure 13.3 (a) A popular limiter circuit. (b) Transfer characteristic of the limiter circuit; L- and L+ are given by Eqs. (13.8) and (13.9), respectively. (c) When Rf is removed, the limiter turns into a comparator with the characteristic shown.*Microelectronic Circuits - Fifth Edition Sedra/Smith5Copyright 2004 by Oxford University Press, Inc.Figure 13.4 A Wien-bridge oscillator without amplitude stabilization.*Microelectronic Circuits - Fifth Edition Sedra/Smith6Copyright 2004 by Oxford University Press, Inc.Figure 13.5 A Wien-bridge oscillator with a limiter used for amplitude control.*Microelectronic Circuits - Fifth Edition Sedra/Smith7Copyright 2004 by Oxford University Press, Inc.Figure 13.6 A Wien-bridge oscillator with an alternative method for amplitude stabilization.*Microelectronic Circuits - Fifth Edition Sedra/Smith8Copyright 2004 by Oxford University Press, Inc.Figure 13.7 A phase-shift oscillator.*Microelectronic Circuits - Fifth Edition Sedra/Smith9Copyright 2004 by Oxford University Press, Inc.Figure 13.8 A practical phase-shift oscillator with a limiter for amplitude stabilization.*Microelectronic Circuits - Fifth Edition Sedra/Smith10Copyright 2004 by Oxford University Press, Inc.Figure 13.9 (a) A quadrature-oscillator circuit. (b) Equivalent circuit at the input of op amp 2.*Microelectronic Circuits - Fifth Edition Sedra/Smith11Copyright 2004 by Oxford University Press, Inc.Figure 13.10 Block diagram of the active-filter-tuned oscillator.*Microelectronic Circuits - Fifth Edition Sedra/Smith12Copyright 2004 by Oxford University Press, Inc.Figure 13.11 A practical implementation of the active-filter-tuned oscillator.*Microelectronic Circuits - Fifth Edition Sedra/Smith13Copyright 2004 by Oxford University Press, Inc.Figure 13.12 Two commonly used configurations of LC-tuned oscillators: (a) Colpitts and (b) Hartley.*Microelectronic Circuits - Fifth Edition Sedra/Smith14Copyright 2004 by Oxford University Press, Inc.Figure 13.13 Equivalent circuit of the Colpitts oscillator of Fig. 13.12(a). To simplify the analysis, Cm and rp are neglected. We can consider Cp to be part of C2, and we can include ro in R.*Microelectronic Circuits - Fifth Edition Sedra/Smith15Copyright 2004 by Oxford University Press, Inc.Figure 13.14 Complete circuit for a Colpitts oscillator.*Microelectronic Circuits - Fifth Edition Sedra/Smith16Copyright 2004 by Oxford University Press, Inc.Figure 13.15 A piezoelectric crystal. (a) Circuit symbol. (b) Equivalent circuit. (c) Crystal reactance versus frequency note that, neglecting the small resistance r, Zcrystal = jX(w).*Microelectronic Circuits - Fifth Edition Sedra/Smith17Copyright 2004 by Oxford University Press, Inc.Figure 13.16 A Pierce crystal oscillator utilizing a CMOS inverter as an amplifier.*Microelectronic Circuits - Fifth Edition Sedra/Smith18Copyright 2004 by Oxford University Press, Inc.Figure 13.17 A positive-feedback loop capable of bistable operation.*Microelectronic Circuits - Fifth Edition Sedra/Smith19Copyright 2004 by Oxford University Press, Inc.Figure 13.18 A physical analogy for the operation of the bistable circuit. The ball cannot remain at the top of the hill for any length of time (a state of unstable equilibrium or metastability); the inevitably present disturbance will cause the ball to fall to one side or the other, where it can remain indefinitely (the two stable states).*Microelectronic Circuits - Fifth Edition Sedra/Smith20Copyright 2004 by Oxford University Press, Inc.Figure 13.19 (a) The bistable circuit of Fig. 13.17 with the negative input terminal of the op amp disconnected from ground and connected to an input signal vI. (b) The transfer characteristic of the circuit in (a) for increasing vI. (c) The transfer characteristic for decreasing vI. (d) The complete transfer characteristics.*Microelectronic Circuits - Fifth Edition Sedra/Smith21Copyright 2004 by Oxford University Press, Inc.Figure 13.20 (a