Apparatus and method for linearizing field effect transistors in the ohmic region

An apparatus comprising:

• a variable resistance circuit configured to generate an output based on an input and a plurality of control signals, the variable resistance circuit comprising a plurality of linear resistance circuits, wherein each linear resistance circuit comprises:
• a field effect transistor having a gate, a source, and a drain, the gate controlled by a control signal of the plurality of control signals, the drain configured to receive the input, and the source configured to drive the output when the field effect transistor is on;
• a first series circuit in parallel with the gate and the source of the field effect transistor, the first series circuit comprising:
• a first capacitor;
• and
• a first switch in series with the first capacitor, wherein the first switch is configured to be on when the field effect transistor is on, and to be off when the field effect transistor is off;
• and
• a second series circuit in parallel with the gate and the drain of the field effect transistor, the second series circuit comprising:
• a second capacitor;
• and
• a second switch in series with the second capacitor, wherein the second switch is configured to be on when the field effect transistor is on, and to be off when the field effect transistor is off;
• wherein each of the plurality of linear resistance circuits is configured to switch the field effect transistor based on one of the plurality of control signals.

A method of using a field effect transistor, the method comprising:

• controlling activation of the field effect transistor based at least partly on one or more control signals, the field effect transistor having a gate, a source, and a drain;
• filtering an input signal with the field effect transistor when the field effect transistor operates in the ohmic region;
• and
• controlling filtering such that:
• a first switch electrically couples a first capacitor in parallel with the gate and the drain of the field effect transistor when the field effect transistor is on, and the first switch does not electrically couple the first capacitor in parallel with the gate and the drain of the field effect transistor when the field effect transistor is off;
• and
• a second switch electrically couples a second capacitor in parallel with the gate and the source of the field effect transistor when the field effect transistor is on, and the second switches does not electrically couple the first capacitor in parallel with the gate and the source of the field effect transistor when the field effect transistor is off.