Voltage to current converter

摘要

In situations where it is desired to provide an extremely accurate output current generated from an input voltage, errors occur in the conversion. Conventional solutions depend upon operational amplifiers and rely upon the availability of both positive and negative reference voltages. When attempting to design an integrated circuit having accurate output currents using only integrated circuit technology the circuit components introduce undesirable errors. These problems have been overcome by an arrangement which includes a current mirror (104, 105) for providing the output current and also for providing a feedback current (101, 102) for use in modifying the current flowing in an input emitter follower (103). Using this approach, the base emitter voltages of the emitter follower transistor and the input transistor of the current mirror are forced to cancel each other. By adjusting the current densities of the two transistors, substantially perfect error compensation is achieved.