Three schemes for linearising the transconductance of the basic differ
ential pair in subthreshold CMOS are examined: (i) multiple asymmetric
differential pairs, (ii) Source degeneration via symmetric diffusers,
and (iii) source degeneration via a single diffuser. Using a maximall
y flat optimising criterion, the linear range of the basic differentia
l pair can be increased by 4-8 times.