Circuit for amplifying a signal representing a variation in resistance of a variable resistance and corresponding sensor
A circuit for amplifying a signal representing a variation in resistance of a variable resistance comprising at least one first load linked to an output terminal of a first transistor whose other terminal is associated with a variable resistance, in such a way as to allow the recovery of the amplified signal at the terminals of the first load.
1. A circuit for amplifying a signal representing a variation in resistance of a variable resistor sensitive to a physical quantity to be measured comprising:
at least a first load connected to an output terminal of a first transistor, an input terminal of the first transistor being connected directly to a reference resistor, and
a second transistor having an input terminal connected directly to the variable resistor and an output terminal connected to a second load,
wherein the circuit is capable of recovering an amplified signal at the terminals of the first load, and wherein
a control electrode of the first transistor is connected directly to both the control electrode and to the output electrode of the second transistor,
the first load comprises a third transistor comprising an output electrode connected to the output electrode of the first transistor,
the second load comprises a fourth transistor comprising an output electrode connected to the output electrode of the second transistor,
a control electrode of the third transistor is connected directly to both a control electrode and to an output electrode of the fourth transistor, and
an input electrode, respectively an output electrode, corresponding either to a source electrode, respectively a drain electrode, of a corresponding transistor for a metal oxide semiconductor (MOS) field effect transistor, or to an emitter electrode, respectively a collector electrode, of the corresponding transistor for a bipolar transistor.
2. A circuit according to claim 1 , wherein the reference resistor is also a variable resistor.
3. A circuit according to claim 1 , wherein each of the first and second loads comprise at least one resistor.
4. A circuit according to claim 3 , wherein the resistors of the first and second loads are variable resistors.
5. A circuit according to claim 1 , wherein each of the first and second loads comprises two transistors.
6. A circuit according to claim 1 comprising a sampler or a switch for sampling or switching the signal corresponding to the variation in resistance, so as to reduce a low-frequency noise of the circuit.
7. A circuit according to claim 6 , wherein the sampler or switch is capable of correlated double sampling (CDS) of the signal corresponding to the variation in resistance.
8. A circuit according to claim 1 comprising a modulator for modulating the amplitude of the signal representing the variation in resistance, so as to reduce the impact of low-frequency noise of the transistors of said circuit.
9. A circuit according to claims 1 comprising a feedback stabilizer for stabilizing bias point and gain of said circuit.
10. A sensor comprising an amplification circuit according to Claim 1 .
11. A sensor according to claim 10 selected from the group consisting of:
a piezoresistive sensor;
a pressure sensor;
a temperature sensor;
an acceleration sensor;
an inclination sensor;
a microphone; and
a magnetic field sensor.
12. The circuit according to claim 1 , wherein the first transistor and the second transistor are MOS field effect transistors or bipolar transistors.
13. A circuit according to claim 1 , wherein the first, the second, the third and the fourth transistors are MOS field effect transistors or bipolar transistors.