Introduction




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. Here we discuss regarding the design of two-stage cmos opamp. The paper consists of understanding of specifications and circuit topology of opamp. Design procedures along with one example of opamp design using tsmc 0.25 um technology with single bias supply 2.5V is also given. Finally the simulation results of hspice simulator with comparison of specifications of opamp are given.

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LOW-POWER LOW-VOLTAGE CHOPPED TRANSCONDUCTANCE AMPLIFIER FOR

the principle and design of a CMOS low-power, lowvoltage, chopped transconductance amplifier, for noise and offset reduction in mixed analogue digital applications. The operation is based on chopping and dynamic element matching, to reduce noise and offset, without excessive increase of the charge injection residual offset. Experimental results show residual offsets of less than 150mV at 100kHz chopping frequency, a signal to noise ratio of 95dB, in audio band, for 100KHz chopping and a THD of -89dB. The power consumption is 594mW. The CMOS technology for mixed signal applications becomes less and less compatible with analog requirements due to the process tuning towards digital needs. As a consequence for analog functions built in digital CMOS the signal swing reduces with power supply and so does the dynamic range.
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