Patent ID: 6298466
Filing Date: 2001-10-02
Classification: H03F

Abstract:
A method for fabricating an operational amplifier having minimum total harmonic distortion comprising the steps of:estimating a gain level of a second stage of the operational amplifier;calculating a transconductance of the second stage of the operational amplifier as a function of the gain level of the second stage and a load resistance of said operational amplifier;calculating a unity gain frequency level for a first stage of said operational amplifier as a function of the load resistance and a load capacitance of said operational amplifier;calculating a one kilohertz gain level of said first stage as a function of the unity gain frequency level of said first stage;calculating an overall one kilohertz gain level as a function of the one kilohertz gain level of the first stage and the gain level of the second stage;calculating a unity gain frequency for said operational amplifier as a function of the one kilohertz gain level;calculating a value of a compensation capacitor for said operational amplifier as a function of a tail current of a differential pair of transistors within said first stage and a slew rate specified for said operational amplifier;calculating a transconductance of a first stage of the operational amplifier as a function of the value of the compensation capacitor and the unity gain frequency of the operational amplifier;determining an overall D.C. gain level as a function of the overall one kilohertz gain level;determining an output resistance of the first stage of the operational amplifier as a function of the overall D.C. gain level, the transconductance of the first stage, the gain level of the second stage;synthesizing transistor sizes and bias current levels of the operational amplifier given the transconductance of the first and second stages, and the output resistance of the first stage;simulating said operational amplifier to determine if said operational amplifier is optimized to exhibit minimum total harmonic distortion;if said operational amplifier is not optimized, repeating the above steps; andif said operational amplifier is optimized, fabricating said operational amplifier.