M. Vandegevel et al., LOW-POWER MOS INTEGRATED FILTER WITH TRANSCONDUCTORS WITH SPOILT CURRENT SOURCES, IEEE journal of solid-state circuits, 32(10), 1997, pp. 1576-1581
It is shown that an MOS weak-inversion differential pair can be linear
ized considerably by replacing the tail current source with a MOSFET b
iased in the weak-inversion triode region. Calculations show that the
transconductance can be kept constant to within +5%/-0% for input volt
ages up to 130 mV. This linearized differential pair is used in a thir
d-order transconductance-C bandpass filter with 18 Hz and 142 Hz cutof
f frequencies, which draws 4.9 nA from a 1.8-V supply. Its dynamic ran
ge is 62 dB and its active area is 0.5 mm(2).