Patent ID: 6369618
Filing Date: 2002-04-09
Classification: G05F

Abstract:
A voltage-to-current converter circuit which provides an exponential output current, having a first and second voltage source, comprising:a first and second differential input terminal; a first differential amplifier stage having a first and second transistor coupled to the respective first and second differential input terminals to receive a respective first and second differential input voltage, said first differential amplifier having a first and second differential output terminal; a third transistor having a collector, a base and an emitter, the collector coupled to a first current source, the base coupled to the second differential output voltage terminal; a fourth transistor having a collector, a base and an emitter, the emitter coupled to the emitter of the third transistor, the base terminal coupled to the first differential output voltage terminal, the collector providing an output terminal for outputting a current; and a feedback circuit coupled to the third and fourth transistors and to the current source for clamping the current source to a predetermined limit; whereby the output current provided by the fourth transistor is proportional to an exponential function of the first differential input voltage and independent of temperature.