Low voltage continuous time tunable high frequency filters based on floating gates and dynamic biasing techniques

This paper presents two low-voltage circuits based on the use of multiple-input floating-gate transistors. The first is a new CMOS low-voltage linear transconductor for Very High Frequency (VHF). It uses multiple-input floating-gate transistors (MIFGTs) in each inverter of the differential structure transconductor presented by Nauta (1992). The proposed transconductor operates under a constant supply as low as 1.2 V. Its transconductance and output resistance are independently tunable, as shown by experimental measurements. This architecture is suitable for use in HF continuous time filters with programmable center frequency and quality factor. Simulation results of a 10.7 MHz and Q=40 g/sub m/-C filter operating with a voltage supply of 1.4 V and with rail-to-rail input swing are presented. The second is a new class of AB output stage for CMOS op-amps with quiescent current control. The proposed stage can be operated with a supply voltage close to a transistor's threshold voltage. Simulation results are provided that show a 15 MHz gain-bandwidth product when used as the second stage of an op-amp with 1.5 V supply voltage.