Operational Amplifiers Lecture 11 Operational Amplifiers Microelectric Circuit by Meiling CHEN

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

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

Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Negative feedback Positive feedback Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Non-ideal cases Ideal OPA characters Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Consider finite open-loop gain Microelectric Circuit by Meiling CHEN

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

Microelectric Circuit by Meiling CHEN Output resistance Microelectric Circuit by Meiling CHEN

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

Microelectric Circuit by Meiling CHEN Exercise 2.6 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Weighted summer Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Exercise D2.8 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Non-inverting amplifier Ideal case: Non-ideal case: Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Voltage follower Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Exercise D2.9 Exercise D2.13 Microelectric Circuit by Meiling CHEN

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

Microelectric Circuit by Meiling CHEN Difference Amplifier Method I: Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Different-mode input Method I: superposition Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Common-mode input CMRR=infinite CMRR=infinite Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Consider the problem of input resistance Differential mode input resistance Microelectric Circuit by Meiling CHEN

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

Microelectric Circuit by Meiling CHEN Remove the point x Microelectric Circuit by Meiling CHEN

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

Microelectric Circuit by Meiling CHEN Frequency response (open-loop) Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Frequency response (closed loop) Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Output voltage saturation Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Slew rate Microelectric Circuit by Meiling CHEN

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

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

Microelectric Circuit by Meiling CHEN Solution 1: Offset-nulling terminals Solution 2: Capacitive coupling (only ac signal be amplified) Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Offset current Input bias currents Input offset current Upper limit R2 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Solution : introducing R3 Microelectric Circuit by Meiling CHEN

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

Microelectric Circuit by Meiling CHEN Integrator & Differentiator Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Miller Integrator Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Consider Vos offset voltage Consider Ios offset current Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Solution : Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Example 2.7 sketch output response Case I: Case II: Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Differentiator Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Problem *2.31 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Problem *2.43 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Problem **2.69 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Problem *2.77 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Problem *2.78 Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Problem C*2.126 Microelectric Circuit by Meiling CHEN

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

Microelectric Circuit by Meiling CHEN Type A: Finite open-loop gain (unknown) Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Type B: Finite open-loop gain =K Microelectric Circuit by Meiling CHEN

Microelectric Circuit by Meiling CHEN Type C: ± ± Microelectric Circuit by Meiling CHEN