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Operational Amplifiers
Lecture 11 Operational Amplifiers Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Topics Ideal op Amplifiers Ideal OPA circuits analysis Non-ideal op amplifiers Non-ideal OPA circuit analysis Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Ideal operational amplifier Ideal OPA characters Infinite input impedance Zero output impedance Infinite bandwidth Infinite open-loop gain Zero common-mode gain (infinite CMRR) Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Negative feedback Positive feedback Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Non-ideal cases Ideal OPA characters Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Consider finite open-loop gain Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Input and output resistance Example 2.1 An impractically large value So we may have the problem of input resistance. Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Output resistance Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Example 2.2 Example 2.2: Comparing with Example 2.1 Design a amplifier with a gain –100 and an input resistance of 1M. Example 2.1: Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Exercise 2.6 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Weighted summer Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Exercise D2.8 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Non-inverting amplifier Ideal case: Non-ideal case: Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Voltage follower Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Exercise D2.9 Exercise D2.13 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Why use difference amplifier ? CMRR ( Common-Mode Rejection ratio ) Different-mode input Common-mode input Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Difference Amplifier Method I: Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Different-mode input Method I: superposition Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Common-mode input CMRR=infinite CMRR=infinite Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Consider the problem of input resistance Differential mode input resistance Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Instrumentation Amplifier Not is differential mode, common mode input can be pass. Defects: Common mode gain=differential mode gain. Resistance have to match. Advantages: Big differential gain Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Remove the point x Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
DC non-ideal characters Finite open loop gain ( finite CMRR) Finite BW Offset voltage Input bias and offset current Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Frequency response (open-loop) Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Frequency response (closed loop) Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Output voltage saturation Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Slew rate Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Offset voltage From the component mismatches in the input differential stage Output = + saturation or - saturation May be positive or negative Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Reduce the allowable signal swing When input is dc we would not know the output is due to vos or signals Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Solution 1: Offset-nulling terminals Solution 2: Capacitive coupling (only ac signal be amplified) Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Offset current Input bias currents Input offset current Upper limit R2 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Solution : introducing R3 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Inverse amplifier Reduce the effect of Vos Reduce the effect of Ios Non-inverse amplifier Reduce the effect of Vos Reduce the effect of Ios Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Integrator & Differentiator Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Miller Integrator Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Consider Vos offset voltage Consider Ios offset current Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Solution : Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Example 2.7 sketch output response Case I: Case II: Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Differentiator Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Problem *2.31 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Problem *2.43 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Problem **2.69 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Problem *2.77 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Problem *2.78 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Problem C*2.126 Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Non-ideal OP amplifiers Type A: Finite open-loop gain (unknown) Type B: Finite open-loop gain = K Type C: Infinite input impedance Zero output impedance Zero common-mode gain Infinite open-loop gain Infinite bandwidth Ideal OPA characters Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Type A: Finite open-loop gain (unknown) Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Type B: Finite open-loop gain =K Microelectric Circuit by Meiling CHEN
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Microelectric Circuit by Meiling CHEN
Type C: Microelectric Circuit by Meiling CHEN
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