Patent ID: 7276957
Filing Date: 2007-10-02
Classification: H03K

Abstract:
1. A circuit for defining a voltage potential of a floating well in which is formed at least one metal-oxide-semiconductor device, the circuit comprising: a sense circuit operative to detect a voltage at a node to which the floating well is connected and to generate a control signal indicative of whether the voltage at the node is substantially within a voltage range, a lower value of the voltage range being substantially equal to a threshold voltage below a first supply voltage of the circuit, an upper value of the voltage range being substantially equal to a threshold voltage above the first supply voltage; and a voltage generator circuit operative to receive the control signal and to generate a bias signal for setting a voltage potential of the well in response to the control signal, the bias signal being controlled throughout the voltage range; wherein the sense circuit comprises; first and second PMOS devices, a first source/drain of the first PMOS device being adapted for connection to the first supply voltage, a first source/drain of the second PMOS device being adapted for connection to the node to which the floating well is connected, a second source/drain of the first PMOS device being connected to a second source/drain of the second PMOS device and forming an output of the sense circuit for generating the control signal, a gate of the second PMOS device being adapted for connection to the first supply voltage, a gate of the first PMOS device being adapted for connection to the node to which the floating well is connected, and bulks of the first and second PMOS devices being adapted for receiving the bias signal; and a resistive element connected between the output of the sense circuit and a second voltage source.