Pico-A/V range CMOS transconductors using series-parallel current division

A fully integrated 0.5-7 Hz CMOS bandpass amplifier

“…Each stage has a low-pass structure (given by G m1 (4) , G m2 (5) , C 2(4) ) similar to that proposed in [2], and a DC cancellation loop (G m3 (6) , C 1 (3) ). The external piezoelectric sensor is modeled as a capacitor (550pF) with an input voltage in series.…”

“…Simple division of the output current of a differential pair by a high ratio has been widely considered an expensive technique in terms of area. However, the use of seriesparallel division of current [4][5] in an OTA allows the implementation of an area-efficient current divider.…”

Series-parallel association of transistors for the reduction of random offset in non-unity gain current mirrors

“…Another interesting example is the use of series-parallel transistors for current division in standard OTAs to obtain extremely low transconductances with an extended linear range [8]. Using adequate design criteria and layout, a significative improvement in offset is obtained compared to usual current division OTAs or current cancellation techniques where offset is a serious limitation [9,10].…”

“…In Table-1 predicted and measured offset of two OTAs of 2.8nS, and 100pS are shown. The OTAs use series-parallel current division as in [8], and linearized differential input pair [11] to achieve ±550mV (measured) linear range at the input [8]. The measured standard deviation in Table-1 was calculated using 10 circuit samples.…”

“…(8) where P, R, Q and S are the number of unitary transistors in series and parallel in each branch. The expected normalized current mismatch standard deviation for this circuit is: to come from the simplification in (1) of distance-related terms [1,2].…”