Cmos transistor driver#

The proposed back-gate driver circuit would apply, to the integrated-circuit substrate, a bias voltage that would ensure that the parasitic BCTs remain in the “off” state at voltages beyond those that would otherwise cause the parasitic transistors to turn on.

The “Smart” Back-Gate Driver Circuit would sense the turn-on voltage of one parasitic BCT and respond by biasing the substrate at a voltage that would keep all the other parasitic BCTs turned off. The problem is complicated by the fact that ionizing radiation causes the accumulation of positive charges in the buried oxide layer of the integrated circuit, and these charges lower the threshold voltages of the parasitic BCT. In a mixed-voltage (high-voltage/low-voltage) SOI CMOS integrated circuit, the turn-on threshold voltages of parasitic BCTs are usually less than the voltage that the high-voltage transistors can withstand heretofore, this fact has made it necessary to limit voltage ratings accordingly. If a high voltage is impressed on the source or drain of this FET, an inversion layer can form just above the buried oxide, allowing current to flow. A Parasitic Back-Channel Transistor (BCT) exists under a typical low-voltage field-effect transistor (FET). Turn-on of the parasitic transistors is unacceptable because it causes short circuits that render the integrated circuit inoperative. The purpose of the back-gate driver circuit is to raise the threshold (turn-on) voltages of parasitic back-channel transistors (BCTs) that unavoidably exist in such an integrated circuit (see Figure 1). As used here, “low voltage” signifies potentials ≤3.3 V, while “high voltage” signifies potentials ≥40 V. A “smart” back-gate driver circuit has been proposed to enable the operation, at voltages higher than were previously possible, of a silicon-on-insulator (SOI) complementary metal oxide/semiconductor (CMOS) integrated circuit that contains both low- and high-voltage transistors energized by corresponding low- and high-voltage power supplies.

Cmos transistor