Operational current to frequency converter

Voltage or current-controlled oscillators with linear tuning characteristics are needed for Analog to Digital Conversion (ADC). The constant of proportionality between its input control-variable (voltage or current) and output frequency is called conversion-gain. We describe an operational current-to-frequency converter that has a large open-loop conversion-gain like in an operational transconductance element in which the input and output variables are dissimilar. The difference between a current-controlled oscillator and current to frequency converter is that the transfer characteristic of the latter passes through the origin. Such a building block is meant for use in negative feedback circuit-configurations. Here the feedback network dominates the closed-loop transfer characteristics. The ability of such a technique to trade gain for improving linearity and reducing process, voltage and temperature variations, is well known. The idea here is to provide a building block to configure ADC's with different resolutions over a wide range of sampling rates below 1 GHz. We present the architecture of such a device and its achievable performance via simulations using the models of a typical 65nm process technology.