Sense amplifiers and sensing methods

A sense amplifier for sensing an impedance between a first terminal of an electrical circuitry and a second terminal of the electrical circuitry, said sense amplifier comprising:

• means for connecting said first terminal to a voltage V1;
• a node;
• means for connecting said node to said second terminal and for thereby connecting said node to said voltage V1 through said circuitry and through said means for connecting said first terminal to the voltage V1;
• means M1 for providing a conductive path C1 between said node and a voltage V2 different from V1;
• means M2 connected to said node and said for controlling a current through said conductive path C1 so that, when the voltage on said node moves away from V2 towards V1, said means M2 increases an impedance of said conductive path C1;
• and
• means for providing a conductive path C2 between said node and said voltage V2;
• wherein said conductive path C2 shuts off when the voltage on said node is at least as close to V2 as a predetermined voltage.

A sense amplifier for sensing an impedance between a first terminal and a second terminal, said sense amplifier comprising:

• means for connecting said first terminal to a voltage V1;
• a variable-impedance device D1 having terminals T11 and T12 and having a control terminal CT1 for controlling a conductivity of a conductive path between the terminals T11 and T12;
• means for connecting said terminal T11 to said second terminal;
• means for connecting said terminal T12 to a voltage V2 different from V1;
• and
• means M1 for generating a reference voltage on said terminal CT1, said means M1 comprising:
• a transistor TR2 having terminals T21 and T22 and having a control terminal CT2;
• means for keeping said control terminal CT2 at said voltage V1;
• means for connecting said terminal T22 to said voltage V2;
• and
• means M2 for connecting said terminal T21 to said to voltage V1 and to said control terminal CT1.

A sense amplifier for sensing an impedance between a first terminal and a second terminal, said sense amplifier comprising:

• means for connecting said first terminal to a voltage V1;
• a variable-impedance device D1 having terminals T11 and T12 and having a control terminal CT1 for controlling a conductivity of a conductive path between said terminals T11 and T12;
• means for connecting said terminal T11 to said second terminal;
• means for connecting said terminal T12 to a voltage V2 different from V1;
• and
• means M1 for generating a reference voltage on said terminal CT1, said means M1 comprising:
• a transistor TR2 having terminals T21 and T22 and having a control terminal CT2;
• means for keeping said control terminal CT2 at said voltage V2;
• means for connecting said terminal T21 to said voltage V1;
• and
• means for connecting said terminal T22 to said control terminal CT1 and to said voltage V2.

A circuit for sensing an impedance between a first terminal of an electrical circuitry and a second terminal of the electrical circuitry, said circuit comprising:

• means for providing a conductive path between said first terminal and a voltage V1;
• a node;
• means connected to said node and said second terminal, for providing a conductive path between said node and said second terminal;
• means for providing a conductive path between said node and a voltage V2 different from V1;
• an amplification stage for amplifying a voltage on said node, said amplification stage having a first power terminal;
• and
• means for providing a conductive path between said first power terminal and said first terminal, wherein during operation of said circuit a voltage on said first terminal varies with the impedance between said first and second terminals.

A circuit for sensing an impedance between a first terminal of an electrical circuitry and a second terminal Of the electrical circuitry, said circuit comprising:

• a node;
• means for connecting said node to a voltage V2;
• means for connecting said node to said second terminal and for thereby connecting said node to said first terminal through said circuitry, so that, during operation of said circuit, a voltage on said node is closer to V2 and farther from a voltage V1 than a voltage on said second terminal;
• an amplification stage comprising:
• a variable-impedance device D1 having terminals T11 and T12 and a control terminal CT1;
• means for connecting said control terminal CT1 to said node;
• and
• means for connecting said terminal T12 to said voltage V2;
• means M1 for connecting said terminal, T11 and said first terminal to said voltage V1 so as to provide a variable-impedance conductive Bath Cl between said terminal T11 and said voltage V1, said means M1 having a control terminal CT such that when a voltage on said control terminal CT moves away from V2 towards V1, a conductivity of said conductive path C1 decreases;
• and
• means for keeping the voltage on said control terminal CT substantially equal to the voltage on said second terminal.

A method for sensing an impedance between a first terminal of an electrical circuitry and a second terminal of the electrical circuitry, said method comprising the steps of:

• providing a current path CP1 between said first terminal and a voltage V1;
• providing a current between said second terminal and a voltage V2 different from V1 through a first current path;
• and
• providing a current between said second terminal and said voltage V2 through a second current path which has a common node with said first current path, so that:
• when said impedance between said first and second terminals increases to its highest value, the current through said second current path decreases to zero while the current through said first current path pulls a voltage on said common node to a predetermined value indicative of said highest value of said impedance;
• and
• when said impedance decreases from its highest value, the current through said second current path increases in magnitude and becomes greater in magnitude than the current through said first current path, wherein at least a portion of the current though the first and second current paths flows through said circuitry and said current path CP1.

A method for sensing an impedance between a first terminal of an electrical circuitry and a second terminal of the electrical circuitry, said method comprising the steps of:

• connecting a node connected to said second terminal to a voltage V2, and connecting said first terminal to a voltage V1 different from V2 thereby connecting said node to said voltage V1 through said circuitry and said first terminal, to provide on said node a voltage indicative of said impedance between said first and second terminals, the voltage on said node being between V1 and V2;
• amplifying the voltage on said node by an inverting amplification stage having a power terminal PT1;
• and
• during amplifying, providing a variable-impedance conductive path between said terminal PT1 and said voltage V1 such, that when said impedance between said first and second terminals decreases to cause the voltage on said node to move away from V2 towards V1, a voltage on said power terminal PT1 moves away from V1 towards V2 to decrease a magnitude of a current through said amplification stage.

A sense amplifier for sensing an impedance between a first terminal and a second terminal, said sense amplifier comprising:

• a transistor T1 for connecting said first terminal to a reference voltage;
• a transistor T2 having a terminal T21 connected to said second terminal and having a terminal T22;
• a transistor T3 for connecting said terminal T22 to a power supply voltage;
• a transistor T4 for connecting said terminal T22 to said power supply voltage;
• a PMOS transistor T5 having a gate connected to said terminal T22;
• an NMOS transistor T6 having a gate connected to said terminal T22 and a drain connected to a drain of said transistor T5;
• and
• a transistor T7 having a terminal connected to a source of said NMOS transistor T6.