High-linearity tunable low-Gm transconductor based on bootstrapping

In this brief, a novel pseudo-differential low-transconductance amplifier is proposed based on the bootstrapping technique. The transconductor is implemented using two voltage follower topologies as amplifiers with their outputs connected to both terminals of a resistor, thus bootstrapping the voltages at these terminals to increase the equivalent resistance value, and achieve a very low transconductance without the need for large passive components. In this way, a highly-linear compact structure is designed whose transconductance can be tuned by external current sources. The circuit was fabricated in a standard 0.18μm CMOS process. The experimental results show a tunable transconductance in the range of tens of nA/V, with a total harmonic distortion lower than -40dB at 350mVpp@1kHz. The power consumption of the amplifier is 4μW under a 1.8V supply voltage.