C H A P T E R 02
Operational Amplifiers Microelectronic Circuits, International Sixth Edition
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Figure 2.1 Circuit symbol for the op amp.
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Figure 2.2 The op amp shown connected to dc power supplies.
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Figure 2.3 Equivalent circuit of the ideal op amp.
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Figure E2.3
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Figure 2.5 The inverting closed-loop configuration.
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Figure 2.6 Analysis of the inverting configuration. The circled numbers indicate the order of the
analysis steps.
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Figure 2.7 Analysis of the inverting configuration taking into account the finite open-loop
gain of the op amp.
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Figure 2.8 Circuit for Example 2.2. The circled numbers indicate the sequence of the steps in the analysis.
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Figure 2.9 A current amplifier based on the circuit of Fig. 2.8. The amplifier delivers its output current to R4. It has
a current gain of (1 + R2 /R3), a zero input resistance, and an infinite output resistance. The load (R4), however,
must be floating (i.e., neither of its two terminals can be connected to ground).
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Figure E2.5
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Figure E2.6
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Figure 2.10 A weighted summer.
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Figure 2.11 A weighted summer capable of implementing summing coefficients of both signs.
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Figure 2.12 The noninverting configuration.
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Figure 2.13 Analysis of the noninverting circuit. The sequence of the steps in the analysis is
indicated by the circled numbers.
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Figure 2.14 (a) The unity-gain buffer or follower amplifier. (b) Its equivalent circuit model.
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Figure E2.9
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Figure E2.13
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Figure 2.15 Representing the input signals to a differential amplifier in terms of their
differential and common-mode components.
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Figure 2.16 A difference amplifier.
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Figure 2.17 Application of superposition to the analysis of the circuit of Fig. 2.16.
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Figure 2.19 Finding the input resistance of the difference amplifier for the case R3 = R1 and R4 = R2.
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Figure 2.20 A popular circuit for an instrumentation amplifier. (a) Initial approach to the circuit (b) The circuit in (a) with the
connection between node X and ground removed and the two resistors R1 and R1 lumped together. This simple wiring change
dramatically improves performance. (c) Analysis of the circuit in (b) assuming ideal op amps.
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Figure 2.22 The inverting configuration with general impedances in the feedback and the feed-in paths.
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Figure 2.23 Circuit for Example 2.4.
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Figure 2.24 (a) The Miller or inverting integrator. (b) Frequency response of the integrator.
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Figure 2.25 The Miller integrator with a large resistance RF connected in parallel with C
in order to provide negative feedback and hence finite gain at dc.
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Figure 2.26 Waveforms for Example 2.5: (a) Input pulse. (b) Output linear ramp of ideal integrator
with time constant of 0.1 ms. (c) Output exponential ramp with resistor RF connected across
integrator capacitor.
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Figure 2.27 (a) A differentiator. (b) Frequency response of a differentiator with a time-constant CR.
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Figure 2.28 Circuit model for an op amp with input offset voltage VOS.
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Figure E2.21 Transfer characteristic of an op amp with VOS = 5 mV.
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Figure 2.29 Evaluating the output dc offset voltage due to VOS in a closed-loop amplifier.
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Figure 2.30 The output dc offset voltage of an op amp can be trimmed to zero by connecting a potentiometer to the
two offset-nulling terminals. The wiper of the potentiometer is connected to the negative supply of the op amp.
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Figure 2.31 (a) A capacitively coupled inverting amplifier. (b) The equivalent circuit for determining its dc output offset voltage VO.
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Figure 2.32 The op-amp input bias currents represented by two current sources IB1 and IB2.
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Figure 2.33 Analysis of the closed-loop amplifier, taking into account the input bias currents.
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Figure 2.34 Reducing the effect of the input bias currents by introducing a resistor R3.
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Figure 2.35 In an ac-coupled amplifier the dc resistance seen by the inverting terminal is R2; hence R3 is chosen equal to R2.
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Figure 2.36 Illustrating the need for a continuous dc path for each of the op-amp input terminals. Specifically, note
that the amplifier will not work without resistor R3.
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Figure 2.37 Determining the effect of the op-amp input offset voltage VOS on the Miller integrator circuit.
Note that since the output rises with time, the op amp eventually saturates.
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Figure 2.38 Effect of the op-amp input bias and offset currents on the performance of the Miller integrator circuit.
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Figure 2.39 Open-loop gain of a typical general-purpose internally compensated op amp.
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Figure 2.40 Frequency response of an amplifier with a nominal gain of +10 V/V.
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Figure 2.41 Frequency response of an amplifier with a nominal gain of 10 V/V.
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Figure 2.42 (a) A noninverting amplifier with a nominal gain of 10 V/V designed using an op amp that saturates at
±13-V output voltage and has ±20-mA output current limits.
(b) When the input sine wave has a peak of 1.5 V, the output is clipped off at ±13 V.
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Figure 2.44 Effect of slew-rate limiting on output sinusoidal waveforms.
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