Importance

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Abstract

An all-MOS voltage to current converter is provided in which the resistor of a conventional voltage to current converter is replaced by one or more transistors. The transistors are all subject to the same process variations, solving the tracking problem that can occur using both analog and digital components. An output current is produced as a linear function of an input voltage using first and second MOSFETs by impressing a first voltage related to the input voltage across the first MOSFET transistor and, while operating the first MOSFET in its linear region, producing a first current through the first MOSFET having a magnitude related to the first voltage. The first voltage is then level-shifted by a predetermined voltage to produce a level-shifted voltage. The level-shifted voltage is applied to the second MOSFET, which is operated in its saturated region, producing a second current through the second MOSFET having a magnitude related to the level-shifted voltage. Currents substantially equal to the first and second currents are added together to produce the output current. A voltage to current converter for producing an output current as a linear function of an input voltage therefore includes a first MOSFET, a second MOSFET connected in diode configuration, and circuitry connected to the input voltage and to the first MOSFET for impressing a first voltage related to the input voltage across the first MOSFET. Level shifter circuitry is connected to the first MOSFET and to the second MOSFET for shifting the first voltage by a predetermined voltage to produce a level-shifted voltage and for applying the level-shifted voltage to the second MOSFET. Circuitry is also provided for adding together currents substantially equal to currents produced in the first and second MOSFETs to produce the output current.

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