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

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Abstract

Two compact ultra low-power CMOS triode transconductor topologies denoted VLPT-gm and Delta-gm are proposed. In both circuits, input transistors are kept in the triode region to benefit from the lowest gm/ID ratio. This allows achieving a small-signal transconductance gm down to hundreds of pA/V, making such transconductors attractive for the synthesis of gm-C filters with cut-off frequencies in the range of Hz and sub-Hz. The gm value is adjusted by a well defined aspect-ratio (W/L) and drain-source voltage VDS, the latter a replica of the tuning voltage VTUNE imposed as drain-source voltage of input devices. VLPT-gm reaches a minimum gm of 1 nA/V, whereas Delta-gm exhibits a gm as low as 400 pA/V. Input-referred noise spectral density is typically 12.33 μV/Hz1/2 @ 1 Hz and 93.75 μV/Hz1/2 @ 1 Hz for VLPT-gm and Delta-gm, respectively. In addition, setting their gm equal to 1 nA/V and arranging them as first-order lossy integrators, Delta-gm presents higher bandwidth with respect to VLPT-gm. Cut-off frequencies are 1.33 kHz and 24 kHz for VLPT-gm and Delta-gm integrators, respectively. Finally, as an application example, both transconductors were used as building blocks to realize a 6th-order wavelet gm-C filter. For both approaches, THD was kept below 1% for signal swings up to 200 mVpp.The design complies with a 1.5 V supply and a 0.35 μm CMOS process and features an overall power consumption of 51 and 114 nW, respectively for VLPT-gm and Delta-gm filters.

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Authors and Affiliations

  1. Electrical Engineering Department, Technological Institute of Aeronautics, Sao Jose dos Campos, SP, Brazil

    Peterson R. Agostinho

  2. Electronics Research Laboratory, Faculty of Electrical Engineering, Delft University of Technology, Delft, The Netherlands

    Peterson R. Agostinho, Sandro A. P. Haddad & Wouter A. Serdijn

  3. Brazil Semiconductor Technology Center, Freescale Semiconductor, 13069-380, Campinas, SP, Brazil

    Sandro A. P. Haddad & Jader A. De Lima

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  1. Peterson R. Agostinho
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  2. Sandro A. P. Haddad
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  3. Jader A. De Lima
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  4. Wouter A. Serdijn
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Correspondence to Jader A. De Lima.

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Agostinho, P.R., Haddad, S.A.P., De Lima, J.A. et al. An ultra low power CMOS pA/V transconductor and its application to wavelet filters. Analog Integr Circ Sig Process 57, 19–27 (2008). https://doi.org/10.1007/s10470-008-9193-6

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  • DOI: https://doi.org/10.1007/s10470-008-9193-6

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