Drain current mismatch in SOI CMOS current mirrors and D/A converters due to localised internal and coupled heating

Matching of transistor behaviour is critical to the functioning of many analogue circuits, and is usually controlled by device area and layout. This paper shows how highly localised heat generation and coupling can significantly alter the matching behaviour in circuits when fabricated in SOI CMOS. Measurements and analyses are presented for simple current mirrors and a current output D/A converter fabricated in 0.7µm SOI CMOS which demonstrate the significance of these effects and how they can be accommodated in design.