| Summary: | 碩士 === 國立交通大學 === 電子工程學系 === 85 === The advantages of using OTA's as building blocks for
larger subthresholdanalog circuits are that (i) the circuit
structures are simple ; and (ii) thecircuits can be implemented
by a standard CMOS process. One of the fundamentalfactors that
limit the accuracy of the subthreshold MOS analog
integratedcircuits is the mismatch in the drain current between
identically drawn andbiased devices . Owing to exponential
dependencies on the process variations ,however , devices in
weak inversion usually exhibit a dramatically large mis-match
in current as compared with that in above-threshold. The non-
zero offsetvoltage is measured of the mismatch in OTA's.
In this paper we extensively measure and analyze the offset
voltage mis-match of the operational transconductance amplifier(
OTA) circuits operating inthe subthreshold region . We treat the
subthreshold offset voltage mismatch ofOTA from a statistical
point of view . A statistical subthreshold OTA offsetvoltage
mis-match model is derived analytically as function of process
para-meter variations , area , and bias . Compared to the
measured data, the devicemismatch model can be used to extract
the variations in the two procee para-meters such as flat band
voltage and body effect coefficients.The subthresholdOTA offset
voltage mis-match has further been successfully predicted by
meansof those extracted process parameter variations.
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