Verification of a Design Procedure for Computer Aided Design of General Purpose Internally Compensated CMOS Operational Amplifiers

Mustafa G. Guvench (USA)


CMOS, operational amplifier, design.


: In this paper a design procedure and successful experimental verification results obtained from it are being reported for implementing internally compensated general purpose operational amplifiers powered from a single power supply and with high gain bandwidth product, good slew-rate, low output impedance and good drive levels. The procedure was developed for an in-house training course on "analog integrated circuit design" as an example of using mathematical tools (MathCad) in the design of analog integrated circuit blocks. The resulting MathCad file became a design automation tool for CMOS OpAmp Design. It is shown that all opamp specs targeted are met or exceeded by the sample opamp designed and fabricated using Fairchild Semiconductor's CS80C CMOS process with the W/L ratios predicted by this tool. Similar successful verification results are being reported for MOSIS fabricated designs. In this work, experimental verification of the results of a design procedure put on silicon, namely that of an internally compensated general purpose CMOS operational amplifier was done including its reference bias current source. The work was done as an example in the CMOS Analog training class taught by the author at Fairchild Semiconductor's Product Development Center. A MathCad file developed by the instructor was used as a design automation tool to calculate W and L parameters of all of the transistors in the circuit as well as resistors and frequency compensation capacitor in a PMOS input CMOS operational amplifier circuit.

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