An adaptive current-to-voltage converter for sensor applications

Aiming at the needs of high sensitivity and wide dynamic range in many sensor applications, we present, in this paper, a structure of current-to-voltage conversion circuit. It is made to be very sensitive to a very weak current signal and to be able to lower its conversion gain if the signal becomes stronger. The variable conversion gain is obtained using the non-linearity of the MOS transistor characteristics. This circuit is designed to use the resistive features of the devices, instead of the transconductances. The circuit consists of only four transistors and can be fabricated in a single poly process.