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
$0.18 ~\mu m$
CMOS process. The experimental results show a tunable transconductance in the range of tens of
$nA/V$
, with a total harmonic distortion lower than
$-40 dB$
at
$350 mVpp\text{@}1kHz$
. The power consumption of the amplifier is
$4 ~\mu W$
under a
$1.8 V$
supply voltage.