An ultra low power CMOS pA/V transconductor and its application to wavelet filters

An ultra low power CMOS pA/V transconductor and its application to wavelet filters

Agostinho, P.R.
Haddad, S.A.P.
De Lima, J.A.
Serdijn, W.A.

Electrical Engineering, Mathematics and Computer Science

Electronics Research Laboratory

2008-06-21

Two compact ultra low-power CMOS triode transconductor topologies denoted VLPT-g(m) and Delta-g(m) are proposed. In both circuits, input transistors are kept in the triode region to benefit from the lowest g(m)/I-D ratio. This allows achieving a small-signal transconductance g(m) down to hundreds of pA/V, making such transconductors attractive for the synthesis of g(m)-C filters with cut-off frequencies in the range of Hz and sub-Hz. The g(m) value is adjusted by a well defined aspect-ratio (W/L) and drain-source voltage V-DS, the latter a replica of the tuning voltage V-TUNE imposed as drain-source voltage of input devices. VLPT-g(m) reaches a minimum g(m) of 1 nA/V, whereas Delta-g(m) exhibits a g(m) as low as 400 pA/V. Input-referred noise spectral density is typically 12.33 mu V/Hz(1/2) @ 1 Hz and 93.75 mu V/Hz(1/2) @ 1 Hz for VLPT-g(m) and Delta-g(m), respectively. In addition, setting their g(m) equal to 1 nA/V and arranging them as first-order lossy integrators, Delta-g(m) presents higher bandwidth with respect to VLPT-g(m). Cut-off frequencies are 1.33 kHz and 24 kHz for VLPT-g(m) and Delta-g(m) integrators, respectively. Finally, as an application example, both transconductors were used as building blocks to realize a 6th-order wavelet g(m)-C filter. For both approaches, THD was kept below 1% for signal swings up to 200 mV(pp). The design complies with a 1.5 V supply and a 0.35 mu m CMOS process and features an overall power consumption of 51 and 114 nW, respectively for VLPT-g(m) and Delta-g(m) filters

Low-frequency filters
CMOS transconductors
gm-C filter
Wavelet filter

http://resolver.tudelft.nl/uuid:b334de08-eb3e-423d-9220-35987d64b116

Springer

1573-1979

Analog Integrated Circuits and Signal Processing, 57 (1-2)

Institutional Repository

journal article

(c) 2008 The Authors