Hanyang University

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Chapter 2. Operational Amplifiers

• Hanyang University
• EECS
• Prof. Myung-Ryul Choi

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2.1 The Op-Amp Terminals
Figure 2.1 Circuit symbol for the op amp.
Figure 2.2 The op amp shown connected to dc
power supplies.
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2.2 The Ideal Op - Amp

• Equivalent circuit of the ideal op amp
• Inverting input terminal
• Non-inverting input terminal
• Common mode rejection
• Differential gain
• Differential input , single ended output
• Open loop gain

Figure 2.3 Equivalent circuit of the ideal op
amp.
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2.3 The Inverting Configuration

• Negative feedback
• Closed loop gain

Figure 2.5 The inverting closed-loop
configuration.
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2.3

• Virtual short circuit
• Virtual ground
• Input and output resistance

(b)
(a)
Figure 2.6 Analysis of the inverting
configuration. The circled numbers indicate the
order of the analysis steps.
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2.3

• Effect of finite open loop gain

Figure 2.7 Analysis of the inverting
configuration taking into account the finite
open-loop gain of the op amp.
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2.4 Other Applications of The Inverting
Configuration

• Inverting integrator

Figure 2.39 (a) The Miller or inverting
integrator. (b) Frequency response of the
integrator.
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2.4

• Differentiator

(a)
Figure 2.44 (a) A differentiator. (b) Frequency
response of a differentiator with a
time-constant CR.
(b)
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2.4

• Weighted summer

Figure 2.10 A weighted summer.
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2.5 The Non inverting Configuration

• Negative feedback
• Equivalent of finite open loop gain

Figure 2.13 Analysis of the non-inverting
circuit. The sequence of the steps in the
analysis is indicated by the circled numbers.
Figure 2.22 Open-loop gain of a typical
general-purpose internally compensated op amp.
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2.5

• Voltage follower

Figure 2.14 (a) The unity-gain buffer or
follower amplifier. (b) Its equivalent circuit
model.
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2.6 Example of Op Amp Circuits

• A difference amplifier

Figure 2.16 A difference amplifier.
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2.6

• An Instrumentation Amplifier

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2.7 Effect of Finite Open Loop Gain Bandwidth
on Circuit performance

• Frequency compensation
• Unity gain bandwidth
• Dominant pole

Figure 2.22 Open-loop gain of a typical
general-purpose internally compensated op amp.
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2.8 Large Signal Operation of Op - Amps

• Output saturation

Figure 1.13 An amplifier transfer characteristic
that is linear except for output saturation.
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2.8

• Slew rate ( SR )

Figure 2.26 (a) Unity-gain follower. (b) Input
step waveform. (c) Linearly rising output
waveform obtained when the amplifier is slew-rate
limited. (d) Exponentially rising output waveform
obtained when V is sufficiently small so that the
initial slope (vtV) is smaller than or equal to
SR.
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2.8

• Full power Bandwidth

Figure 2.27 Effect of slew-rate limiting on
output sinusoidal waveforms.
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2.9 DC Imperfections

• Input offset voltage

Figure 2.28 Circuit model for an op amp with
input offset voltage VOS.
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2.9

• Input bias current

Figure 2.32 The op-amp input bias currents
represented by two current sources IB1 and IB2.