Design report of two stage cmos operational amplifier using tsmc 0.25 um
Operational Amplifier is the most common building blocks of most of the electronics system may not need introduction. They are integral part of many analog and mixed signal systems. Opamps with vastly different level of complexity are used to realize functions ranging from dc bias generation to high gain amplification, filtering or ADCs. The design of opamp continues to pose a challenge as the supply voltage and transistor channel lengths scale down with each generation of CMOS technology. Opamp consists of one or more differential stages and usually followed by additional gain stages depending upon the requirements.
Specifications of opamp
The design starts with the understanding of the specifications. Some common definitions of operational amplifier specifications are given below. The design specs are given in table no 1.
Open Loop Gain: It is the ratio between output voltage and differential input voltage. The output signal is much larger than the input signal, so it is commonly called as large signal voltage gain.
Slew Rate: The maximum rate of change of output voltage per unit time. (dVout/dt) The slope of the out put signal is the slew rate.
Rise time : the time required by the output to go from 10% to 90% of its final value is called the rise time.
Overshoot: The maximum amount by which the output deviate form its steady state value is the overshoot.
CMRR: Common Mode Rejection ratio is the ratio between differential gain and common mode gain.
Power Dissipation: The amount of power dissipated. It is the product of voltage and total current in the circuit.
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