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Lecture 9
March 30, 2015
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EEE 312 Electronic Circuits
In the high-frequency region, the capacitive elements of importance are the
interelectrode (between-terminals) capacitances internal to the active device
and the wiring capacitance between leads of the network. The large
capacitors of the network that controlled the low- frequency response are all
replaced by their short-circuit equivalent due to their very low reactance
levels.
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MILLER EFFECT CAPACITANCE
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For inverting amplifiers (phase shift of 180° between input and output, resulting in a
negative value for Av), the input and output capacitance is increased by a
capacitance level sensitive to the interelectrode capacitance between the input and
output terminals of the device and the gain of the amplifier. In Fig. 9.42, this
“feedback” capacitance is defined by Cf.
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MILLER EFFECT CAPACITANCE
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MILLER EFFECT CAPACITANCE
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For any inverting amplifier, the input capacitance will be increased by a
Miller effect capacitance sensitive to the gain of the amplifier and the
interelectrode (parasitic) capacitance between the input and output terminals
of the active device.
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MILLER EFFECT CAPACITANCE
The Miller Effect Output Capacitance
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MILLER EFFECT CAPACITANCE
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The Miller Effect Output Capacitance
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MILLER EFFECT CAPACITANCE
The Miller Effect Output Capacitance
For noninverting amplifiers such as the common-base and emitter-follower
configurations, the Miller effect capacitance is not a contributing concern
for high-frequency applications.
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MILLER EFFECT CAPACITANCE
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• At the high-frequency end, there are two factors that define the3-dB cutoff point: the network capacitance (parasitic and
introduced) and the frequency dependence of hfe(β).
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HIGH-FREQUENCY RESPONSE—BJT AMPLIFIER
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HIGH-FREQUENCY RESPONSE—BJT AMPLIFIER
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HIGH-FREQUENCY RESPONSE—BJT AMPLIFIER
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HIGH-FREQUENCY RESPONSE—BJT AMPLIFIER
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HIGH-FREQUENCY RESPONSE—BJT AMPLIFIER
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Problems
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Problems
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Problems
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Problems
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Problems
