Method and apparatus for reducing parasitic bipolar current in a silicon-on-insulator transistor

An apparatus for reducing parasitic bipolar current in a field effect transistor (“FET”), comprising:

• a first p-type FET (“PFET”) having a body disposed, at least in part, on an insulator;
• and
• control circuitry coupled to the body and the gate of the first PFET, wherein the control circuitry comprises:
• a body-charge control PFET, having first and second conducting electrodes and a gate electrode, wherein the body-charge control PFET first conducting electrode is electrically coupled to the body of the first PFET, and the body-charge control PFET second conducting electrode is electrically coupled to an electrical source;
• and
• an inverter having an inverter input electrically coupled to the body-charge control PFET gate electrode, and an inverter output electrically coupled to the first PFET gate electrode, wherein the control circuitry controls charge on the first PFET solely responsive to a voltage applied directly to the body-charge control PFET gate, wherein the voltage applied to the body-charge control PFET gate electrode being above a certain first voltage level tends to turn off the body-charge control PFET and electrically isolate the body from the source, thereby permitting the body to float and a charge to accumulate on the body, and the voltage applied to the body-charge control PFET gate electrode being below a certain second voltage level tends to turn on the body-charge control PFET and electrically couple the body to the source, thereby discharging at least a portion of any charge accumulated on the body.

Control circuitry for a complementary passgate device, the device having a first p-type, field effect transistor “(PFET”), the first PFET having a body disposed, at least in part, on an insulator, and a first n-type field effect transistor “(NFET”), the first NFET having a body disposed, at least in part, on an insulator, the control circuitry consisting of:

• an inverter;
• and
• a body-charge control NFET, having first and second conducting electrodes and a gate electrode, wherein the body-charge control NFET first conducting electrode is electrically coupled to the body of the first NFET, and the body-charge control NFET second conducting electrode is electrically coupled to an electrical sink, wherein an input of the inverter is electrically coupled to a gate electrode of the first NFET, and an output of the inverter is electrically coupled to the body-charge control NFET gate electrode and a gate electrode of the first PFET, so that a voltage applied to the first NFET gate electrode being above a certain first voltage level tends to turn on the first NFET, and drive the inverter output voltage low, tending to turn on the first PFET and turn off the body-charge control NFET, permitting the body of the first NFET to float and charge to accumulate on the body of the first NFET, and the voltage applied to the first NFET gate electrode being below a certain second voltage level tends to turn off the first NFET, and drive the inverter output voltage high, tending to turn off the first PFET and turn on the body-charge control NFET, discharging any charge accumulated on the body of the first NFET.

Control circuitry for a complementary passgate device, the device having a first p-type, field effect transistor “(PFET”), the first PFET having a body disposed, at least in part, on an insulator, and a first n-type field effect transistor “(NFET”), the first NFET having a body disposed, at least in part, on an insulator, the control circuitry consisting of:

• an inverter;
• a body-charge control NFET, having first and second conducting electrodes and a gate electrode, wherein the body-charge control NFET first conducting electrode is electrically coupled to the body of the first NFET, and the body-charge control NFET second conducting electrode is electrically coupled to an electrical sink,
• a body-charge control PFET, having first and second conducting electrodes and a gate electrode, wherein the body-charge control PFET first conducting electrode is electrically coupled to the body of the first PFET, the body-charge control PFET second conducting electrode is electrically coupled to an electrical source, wherein an input of the inverter is coupled to a gate electrode of the first NFET and the body-charge control PFET gate electrode, and an output of the inverter is electrically coupled to the body-charge control NFET gate electrode and a gate electrode of the first PFET, so that a voltage applied to the first NFET gate electrode being above a certain first voltage level tends to i) turn on the first NFET and turn off the body-charge control PFET, permitting the body of the first PFET to float and charge to accumulate on the body of the first PFET, and ii) drive the inverter output voltage low, tending to turn on the first PFET and turn off the body-charge control NFET, permitting the body of the first NFET to float and charge to accumulate on the body of the first NFET, and the voltage applied to the first NFET gate electrode being below a certain second voltage level tends to i) turn off the first NFET and turn on the body-charge control PFET, discharging any charge accumulated on the body of the first PFET, and ii) drive the inverter output voltage high, tending to turn off the first PFET and turn on the body-charge control NFET, discharging any charge accumulated on the body of the first NFET.

A method for controlling a complementary passgate device, the device having a first p-type, field effect transistor “(PFET”), the first PFET having a body disposed, at least in part, on an insulator, and a first n-type field effect transistor “(NFET”), the first NFET having a body disposed, at least in part, on an insulator, the method consisting of the steps of:

• applying a first voltage level to the first NFET gate electrode, wherein a body-charge control NFET has a first conducting electrode electrically coupled to the body of the first NFET, and a second conducting electrode electrically coupled to an electrical sink, and an input of an inverter is electrically coupled to a gate electrode of the first NFET, and an output of the inverter is electrically coupled to the body-charge control NFET gate electrode and a gate electrode of the first PFET, wherein the first voltage level tends to turn on the first NFET, and drive an inverter output voltage low, tending to turn on the first PFET and turn off the body-charge control NFET, permitting the body of the first NFET to float and charge to accumulate on the body of the first NFET;
• applying a second voltage level to the first NFET gate electrode, wherein the second voltage level tends to turn off the first NFET, and drive the inverter output voltage high, tending to turn off the first PFET and turn on the body-charge control NFET, discharging any charge accumulated on the body of the first NFET.

A method for turning on and off a complementary passgate device, the device having a first p-type, field effect transistor “(PFET”), the first PFET having a body disposed, at least in part, on an insulator, and a first n-type field effect transistor “(NFET”), the first NFET having a body disposed, at least in part, on an insulator, the method consisting of the steps of:

• applying a first voltage level to the first NFET gate electrode, wherein a body-charge control NFET has a first conducting electrode electrically coupled to the body of the first NFET, and a second conducting electrode electrically coupled to an electrical sink, wherein a body-charge control PFET has a first conducting electrode electrically coupled to the body of the first PFET, and a second conducting electrode electrically coupled to an electrical source, wherein an input of an inverter is electrically coupled to a gate electrode of the first NFET and the body-charge control PFET gate electrode, and an output of the inverter is electrically coupled to the body-charge control NFET gate electrode and the first PFET gate electrode, and wherein the first voltage level tends to i) turn on the first NFET and turn off the body-charge control PFET, permitting the body of the first PFET to float and charge to accumulate on the body of the first PFET, and ii) drive the inverter output voltage low, tending to turn on the first PFET and turn off the body-charge control NFET, permitting the body of the first NFET to float and charge to accumulate on the body of the first NFET;
• and
• applying a second voltage level to a gate electrode of the first NFET gate electrode, wherein the second voltage level tends to i) turn off the first NFET and turn on the body-charge control PFET, discharging any charge accumulated on the body of the first PFET, and ii) drive the inverter output voltage high, tending to turn off the first PFET and turn on the body-charge control NFET, discharging any charge accumulated on the body of the first NFET.