PTAT CMOS Current Sources Mismatch over Temperature
Andre Luiz Aita and Cesar Ramos Rodrigues
The 26th Symposium on Integrated Circuits and System Design (SBCCI 2013)
Curitiba - Brazil, September 2nd to 6th, 2013
Proportional to Absolute Temperature (PTAT) CMOS current sources are widely used in temperature sensors, bandgap references, and other temperature-compensating circuits. Most of these applications strongly rely on the accuracy of a current ratio m established with a set of 1+m PTAT current sources. However, a PTAT CMOS current source has a temperature-dependent bias point, which in turn, has a well-known effect on the mismatch of CMOS current sources. This paper analyzes the mismatching properties of PTAT current sources due to variation of the current-sources bias point (gm/IDS) with temperature, from -55oC to 125oC. After the analysis, the paper shows measurements of a precision temperature sensor without mismatch compensation to corroborate the analysis developed.
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