A low voltage cascode biasing circuit with gain-boosting

This paper proposes a new cascode current source circuit that provides high-gain with improved headroom and is suitable for low-voltage amplifiers. The circuit achieves this by modifying a low-voltage cascode gate biasing circuit (“trickle-bias”) such that it amplifies the voltage of the cascode node using a PMOS input folded gain-boost amplifier. The low-voltage current source operates down to 260 mV while providing an improvement of output impedance by a factor of 2.5 as compared to a conventional current source. The proposed cascode current source has been applied to an NMOS input folded-cascode amplifier that gives a gain of 63 dB with a unity-gain frequency of 22.1 MHz at a phase-margin of 64.8° with a total bias current of 30μA operating at a supply voltage of 1.8V.