WAC 1011
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`Library of Congress Cataloging-in-Publication Data
`
`
`
`PRE
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`.
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`ORG
`
`1. Smith.
`
`Sedra. Adel S.
`Microelectronic circuits / Adel S. Sedra. Kenneth C. Smith. ~—- 4th ed.
`p.
`cm. — (Oxford series in electrical and computer engineering)
`includes bibliographical references and index.
`ISBN 0-19-511663-l
`2. Integrated circuits.
`1. Electronic circuits.
`Kenneth Carless.
`ll Title.
`111. Series.
`TK7867.S39
`1997
`o1l.38l——dc21
`
`_
`
`97-11254
`C113
`
`987654
`
`Printed in the United States of America on acid—free paper
`
`Cover Illustration: The chip shown is the ADXL-50 su1face—micromachined accelerometer. For the first time, sensor
`and signal conditioning are combined on a single monolithic chip. In its earliest application. it was a key factor in
`the improved reliability and reduced cost of modern automotive airbag systems. Photo reprinted with permission of
`Analog Devices. Inc.
`
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`

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`
` ‘Ud:0,
`US<VDO
`(3.63a)
`(3.63b)
`
`
`
`
`
`
`The transfer characteristic represented by these equations is sketched in Fig. 3.37(c). In
`many applications, rD << R and the second equation can be simplified to
`
`
`
` ‘U0 2 ‘U5 "‘ VDO
`
`where VD0 = 0.7 or 0.8 V. Figure 3.37(d) shows the output voltage obtained when the input
`vs is a sinusoi
`
`.
`
`.
`
`xi
`
`
`A the rectifier circuit of Fig. 3.37(a) we observe that when US is
`7
`.
`negative the diode will be cut off and v0 will be zero. It follows that the
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` It is usually prudent, however, to select a diode that has a reverse breakdown voltage at
`least 50% greater than the expected PIV.
`Before leaving the half-wave rectifier, the reader should note two points. First, it is
`possible to use the diode exponential characteristic to determine the exact transfer charac-
`teristic of the rectifier (see Problem 3.82). However, the amount of work involved is usually
`too great to be justified in practice. Of course, such an analysis can be easily done using a
`computer circuit-analysis program such as SPICE (see Section 3.10 and Appendix C).
`Second, whether we analyze the circuit accurately or not it should be obvious that this
`circuit does not function properly when the input signal is small. For instance, this circuit
`
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`180
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`
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`DIODES
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`
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`the pulsating waveform indicated in Fig. 3.36. Although this waveform has a nonzero av-
`erage or a dc component, its pulsating nature makes it unsuitable as a do so ce r electronic
`
`circuits, hence the need for a filter
`"
`'
`
`ii
`ig.
`.
`T
`_ U
`1
`n the following we shall study
`number of recti er circuits and a simple implementation of the output filter.
`
`
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`Alternatively,
`,
`._
`s_,_
`.
`.
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`an integrated-circuit (IC) regulator can be used [see, for example, Soclof (l985)].
`
`The Half-=-Wave Rectifi -'
`
`- . Figure 3.37(a)
`.
`.
`9..
`
`shows the circuit of a half-wave rectifier. This circuit was analyzed in Section 3.1 (‘see Fig.
`3.3) assuming an ideal diode. Using the more realistic battery-plus—resistance diode model,
`we obtain the equivalent circuit shown in Fig. 3.37(b), from which we can write
`
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`

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`
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`(d)
`
`(b) Equivalent circuit of the half-wave rectifier with the diode ‘
`Fig. 3.37 (a) Half~wave rectifier.
`replaced with its battery-plus—resistance model.
`(as) Transfer characteristic of the rectifier
`circuit.
`(d) Input and output waveforms, assuming that rD << R.
`
`181
`
`+
`ac line
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`voltage
`
`(a)
`
`(b)
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`
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`1!‘
`
`IZCYO av-
`
`:lectronic
`
`
`l sdy a
`
`
`
`he filter,
`
`Qnd to
`raused b
`
`fnati vely,
`
`: 3.37(a)
`(see Fig.
`e model,
`
`(3.63a)
`
`(3.63b)
`
`u7(c). In
`
`(3.64)
`
`he input
`
`
`
`tage at
`
`;t, it is
`:harac-
`
`Jsually
`ising a
`1).
`at this
`circuit