# Chap. 5 The Operational Amplifier

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Chap. 5 The Operational Amplifier
2018/11/15 Chap. 5 The Operational Amplifier Contents 5.1 Operational Amplifier Terminals 5.2 Terminal Voltages and Currents 5.3 The Inverting-Amplifier Circuit 5.4 The Summing-Amplifier Circuit 5.5 The Noninverting-Amplifier Circuit 5.6 The Difference-Amplifier Circuit 5.7 A More Realistic Model for the OP Amplifier Objectives 能指明和描述運算放大器的五個端子，並應用電壓和 電流的限制予以簡化，導出一理想運算放大器。 2.能分析包含理想放大器的簡單電路，並分辨下列運算 放大器電路：反相放大器、和值放大器、非反相放大器 與差值放大器。 3.了解比較實際的運算放大器模型，並能利用它來分析包 含這些放大器的簡單電路。

5.1 Operational Amplifier Terminals

5.2 Terminal Voltages and Currents
The voltage transfer characteristic of an op amp. 運算放大器的電壓轉移曲線：當它在線性區運作時，輸出電壓為輸入電壓之差再乘以A 倍，此倍數稱為增益(gain)。 線性區外則輸出電壓是飽和的。 3

Input Voltage Constraint For Ideal Op Amp
2018/11/15 Input Voltage Constraint For Ideal Op Amp 理想運算放大器的輸入電壓限制條件： 在線性區時，因增益無限大，所以vp = vn，亦稱為虛短路(virtual short)。 Input Current Constraint For Ideal Op Amp 理想運算放大器的輸入電流限制條件： 因等效輸入電阻無限大，所以ip = in = 0。 Symbol without the power supply terminals. From KCL, 4 4

EX 5.1 Analyzing an Op Amp Circuit
2018/11/15 EX 5.1 Analyzing an Op Amp Circuit a) Calculate vo if va = 1V and vb = 0V. b) Repeat (a) for va = 1V and vb = 2V. c) If va = 1.5V, specify the range of vb that avoids amplifier saturation. Ideal Negative feedback  linear region No negative feedback  saturation Then analyze and check! a) Because vo lies between ± VCC, the op amp is in its linear region. b) c) 5 5

5.3 The Inverting-Amplifier Circuit
Ideal Note: 6

Open-Loop Operation of an Inverting Amp
Open-Loop Gain of the Op Amp Ideal Note: The op amp can operate open loop in the linear mode only if Also note that : 7

5.4 The Summing-Amplifier Circuit
Ideal @inverting input terminal: & 8

5.5 The Noninverting-Amplifier Circuit
Ideal & & 9

5.6 The Difference-Amplifier Circuit
Ideal @inverting input terminal: If 簡化的差值放大器 輸入電壓與輸出電壓關係 10

The Difference Amplifier-Another Perspective

Measuring Difference-Amplifier Performance

5.7 A More Realistic Model for the Op Amp

Analysis of an Inverting-Amplifier Circuit Using the More Realistic Op Amp Model
14

Analysis of a Noninverting-Amplifier Circuit Using the More Realistic Op Amp Model
where What if Ro0, A, and Ri ? 15

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