# COMPARE IDEAL AND PRACTICAL opamp Done by Alice

COMPARE IDEAL AND PRACTICAL op-amp Done by: Ø Alice Lee Fong Lin Ø Foon Jia Yin Ø Goh Wen Jun Ø Lee Hoi Leong Ø Sin Kit Yeng Ø Yap Cheng Yee 091150076 091150269 091150278 091150431 091151302 091151529

Op-amp concepts

Ideal Versus Practical Ideal characteristics are used to understand simplify the analyses. Practically impossible to achieve these standards. Ideal Practical Open Loop gain A 105 Bandwidth BW 10 -100 Hz Input Impedance Zin >1 M 0 10 -100 Depends only on Vd = (V+ V ) Differential mode signal Depends slightly on average input Vc = (V++V )/2 Common. Mode signal 10 -100 d. B Output Impedance Zout Output Voltage Vout CMRR

Ideal OP-AMP Av = ∞ Vin Zin = ∞ + Av. Vin Zout = 0 Vout

Properties Infinite voltage gain Infinite input impedence Zero output impedence Infinite bandwidth Zero input offset voltage (i. e. exactly zero out when zero in) Zero noise contribution Infinite slew rate Infinite CMRR Infinite power supply rejection ration

Their characteristics can be summarized by the two “Golden rules” The output attempts to do whatever is necessary to make the voltage difference between the inputs zero. The input draws no current.

Practical op-amp

Properties Suffer from several non-ideal effects: Finite voltage gain Finite bandwidth Finite input impedences Non-zero output impedences Finite CMRR Noise

Limitations v. The input current is not exactly zero. v. There are voltage gain limitations including phase shifts. v. There is a finite slew rate. v. There is some temperature differences.

- Slides: 9