Low distortion impedance selection and tunable impedance circuits

A tunable impedance circuit for connecting one or more impedances to, and improving the distortion performance of, a resonant circuit, comprising:

• a fixed impedance;
• an impedance selection circuit to connect first and second impedances in parallel with the fixed impedance, the impedance selection circuit comprising:
• the first impedance connected to a first interface terminal;
• the second impedance connected to a second interface terminal;
• a plurality of series-connected transistors connected between the first and second impedances and configured to connect the first and second impedances electrically in parallel with the fixed impedance when turned on and disconnect the first and second impedances from being electrically in parallel with the fixed impedance when turned off;
• a plurality of drive impedance networks connected to gates, sources, drains, bodies, and isolation regions of the series-connected transistors, the plurality of drive impedance networks including:
• a gate drive impedance network having a plurality of gate drive resistors, each gate drive resistor connected between a gate of a respective one of the plurality of series-connected transistors and a common gate control line and having an impedance magnitude greater than impedance magnitudes of gate-to-source and gate-to-drain capacitances of the respective series-connected transistor at a resonant frequency of the resonant circuit;
• and
• a body drive impedance network having a plurality of body drive resistors, each body drive resistor connected to a body of a respective one of the plurality of series-connected transistors;
• and
• a control circuit connected to the plurality of drive impedance networks to turn on and turn off the series-connected transistors.