Abstract
A magnetic operational amplifier having a differential stage includes a first magnetic field effect transistor MAGFET and a differential signal conditioner, the differential signal conditioner including a load stage, a differential input pair connected to the load stage and a biasing current source connected to the differential input pair; the magnetic field effect transistor MAGFET being connected to the load stage as a second differential input pair and the differential signal conditioner including a second biasing current source connected to the magnetic field effect transistor MAGFET.
Claims
1. A magnetic operational amplifier having a differential stage comprising: a first magnetic field effect transistor MAGFET and a differential signal conditioner comprising: a load stage, a differential input pair connected to the load stage and a biasing current source connected to the differential input pair, wherein the first magnetic field effect transistor MAGFET is connected to the load stage as a second differential input pair and wherein the differential signal conditioner comprises a second biasing current source connected to the magnetic field effect transistor MAGFET.
2. The magnetic operational amplifier according to claim 1, wherein the first magnetic field effect transistor MAGFET is an n-type magnetic field effect transistor MAGFET.
3. The magnetic operational amplifier according to claim 1, wherein the differential signal conditioner comprises at least one differential amplification stage to further amplify a useful signal.
4. The magnetic operational amplifier according to claim 1, wherein the differential signal conditioner further comprises a chopper to eliminate the offset and low-frequency noise of the differential signal conditioner, the chopper comprising a first stage of modulation of a useful signal and a second stage of demodulation of the useful signal, the useful signal entering the second stage of demodulation being a voltage.
5. The magnetic operational amplifier according to claim 3, wherein the second stage of demodulation of the chopper is placed after the last differential amplification stage to eliminate the offset and low-frequency noise of the differential signal conditioner and of each differential amplification stage.
6. The magnetic operational amplifier according to claim 1, further comprising a magnetic sensor connected to the load stage as a second differential input pair and having: a first configuration corresponding to the first magnetic field effect transistor MAGFET, a second configuration corresponding to a second magnetic field effect transistor MAGFET, a third configuration corresponding to a third magnetic field effect transistor MAGFET and a fourth configuration corresponding to a fourth magnetic field effect transistor MAGFET, and wherein the differential signal conditioner further comprises a spinning current module to eliminate the offset and low-frequency noise of the magnetic sensor, the spinning current module periodically alternating the first, second, third and fourth configurations of the magnetic sensor.
Description
BRIEF DESCRIPTION OF THE FIGURES
[0044] FIG. 1 illustrates the structure of a classical differential amplifier stage.
[0045] FIG. 2 illustrates a first differential stage of a magnetic operational amplifier MOP based on a magnetic field effect transistor MAGFET, according to the previous art.
[0046] FIG. 3 illustrates a second differential stage of a magnetic operational amplifier MOP based on a magnetic field effect transistor MAGFET, according to the previous art.
[0047] FIG. 4 illustrates a third differential stage of a magnetic operational amplifier MOP based on a magnetic field effect transistor MAGFET, according to the previous art.
[0048] FIG. 5a illustrates a differential stage of a magnetic operational amplifier MOP based on a first magnetic field effect transistor MAGFET, according to a first embodiment of the invention.
[0049] FIG. 5b illustrates a differential stage of a magnetic operational amplifier MOP based on a first magnetic field effect transistor MAGFET, according to a second embodiment of the invention.
[0050] FIG. 5c illustrates a differential stage of a magnetic operational amplifier MOP based on a first magnetic field effect transistor MAGFET, according to a third embodiment of the invention.
[0051] FIG. 5d illustrates a differential stage of a magnetic operational amplifier MOP based on a first magnetic field effect transistor MAGFET, according to a fourth embodiment of the invention.
[0052] FIG. 6 illustrates the differential stage of a magnetic operational amplifier MOP based on a first magnetic field effect transistor MAGFET according to an embodiment of the invention, associated to differential amplification stages.
[0053] FIG. 7a illustrates the differential stage of a magnetic operational amplifier MOP based on a first magnetic field effect transistor MAGFET according to an embodiment of the invention, associated to a chopper.
[0054] FIG. 7b illustrates the differential stage of a magnetic operational amplifier MOP based on a first magnetic field effect transistor MAGFET according to an embodiment of the invention, associated to differential amplification stages and to a chopper.
[0055] FIG. 8 illustrates a magnetic sensor having four possible symmetric MAGFET configurations.
[0056] FIG. 9a illustrates a first configuration of the magnetic sensor of FIG. 8, corresponding to the first magnetic field effect transistor MAGFET of FIGS. 5a, 5b, 5c and 5d.
[0057] FIG. 9b illustrates a second configuration of the magnetic sensor of FIG. 8, corresponding to a second magnetic field effect transistor MAGFET.
[0058] FIG. 9c illustrates a third configuration of the magnetic sensor of FIG. 8, corresponding to a third magnetic field effect transistor MAGFET.
[0059] FIG. 9d illustrates a fourth configuration of the magnetic sensor of FIG. 8, corresponding to a fourth magnetic field effect transistor MAGFET.
[0060] FIG. 10 illustrates the differential stage of a magnetic operational amplifier MOP based on the magnetic sensor of FIG. 8 having four possible symmetric MAGFET configurations, associated to a spinning current module.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0061] Some embodiments of apparatus and methods in accordance with embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings. The description is to be regarded as illustrative in nature and not as restricted.
[0062] FIG. 1, FIG. 2, FIG. 3 and FIG. 4 have been previously described.
[0063] FIG. 5a shows a differential stage 1 of a magnetic operational amplifier MOP according to a first embodiment of the invention. The differential stage 1 comprises a first magnetic field effect transistor MAGFET 11 and a differential signal conditioner. The first MAGFET 11 has a source S, a first drain D1 and a second drain D2, a gate voltage Vgate. The differential signal conditioner comprises: [0064] a load stage 151, [0065] a differential input pair 153 connected to the load stage 151, [0066] a biasing current source 155 connected to the differential input pair 153 and [0067] a second biasing current source 156 connected to the first MAGFET 11.
[0068] The biasing current source 155 injects and maintains a constant biasing current Ipol in the differential input pair 153. The first MAGFET 11 is connected to the load stage 151 as a second differential input pair. The second biasing current source 156 injects and maintains a constant second biasing current Ipol2 in the first MAGFET 11. According to the first embodiment of the invention, the first magnetic field effect transistor MAGFET 11 is an n-type magnetic field effect transistor MAGFET and the differential input pair 153 is an n-type differential input pair.
[0069] FIG. 5b shows a differential stage 1 of a magnetic operational amplifier MOP according to a second embodiment of the invention, wherein the first magnetic field effect transistor MAGFET 11 is n-type magnetic field effect transistor MAGFET and the differential input pair 153 is a p-type differential input pair.
[0070] FIG. 5c shows a differential stage 1 of a magnetic operational amplifier MOP according to a third embodiment of the invention, wherein the first magnetic field effect transistor MAGFET 11 is a p-type magnetic field effect transistor and the differential input pair 153 is a p-type differential input pair.
[0071] FIG. 5d shows a differential stage 1 of a magnetic operational amplifier MOP according to a fourth embodiment of the invention, wherein the first magnetic field effect transistor MAGFET 11 is p-type magnetic field effect transistor and the differential input pair 153 is an n-type differential input pair.
[0072] The differential stage 1 of the magnetic operational amplifier MOP may be associated to at least one amplification stage Amp1. FIG. 6 shows the differential stage 1 of a magnetic operational amplifier MOP according to an embodiment of the invention, associated to N differential amplification stages Amp1, AmpN with N a natural number greater than or equal to 2.
[0073] FIG. 7a shows the differential stage 1 of a magnetic operational amplifier MOP according to an embodiment of the invention, wherein the differential signal conditioner further comprises a chopper comprising a first stage 157 of modulation of a useful signal and a second stage 158 of demodulation of the useful signal.
[0074] FIG. 7b shows the differential stage 1 of a magnetic operational amplifier MOP according to an embodiment of the invention, associated to at least one amplification stage Amp1, and wherein the differential signal conditioner comprises the chopper having the first stage 157 of modulation of a useful signal and the second stage 158 of demodulation of the useful signal.
[0075] FIG. 8 shows a magnetic sensor 20 based on the use of four MOS transistors arranged in two parallel pairs crossing each other in order to form a pattern inscribed in a square. The magnetic sensor 20 comprises a square gate G that is common to all transistors. At each angle of the square gate G, two perpendicular contacts of the original transistors are connected so as to form a so called angle-contact. The magnetic sensor 20 thus comprises four angle-contacts positioned at each angle of the square gate G: a first angle-contact A, a second angle-contact B, a third angle-contact C and a fourth angle-contact D. The structure of such a magnetic sensor is for example further described in the article A Novel Chopping-Spinning MAGFET Device, by V. Frick et al. (2010).
[0076] By electronically connecting two adjacent angle-contacts together to create a source and leaving the remaining two angle-contacts independent to create split drains, one creates a split-drain MAGFET structure where the source is twice the width of each drain. The symmetry of the magnetic sensor 20 allows creating four identical MAGFET devices in four perpendicular directions.
[0077] FIG. 9a illustrates a first configuration of the magnetic sensor 20, wherein the third angle-contact C and the fourth angle-contact D are connected together to form a source, the first angle-contact A is a first drain and the second angle-contact B is a second drain. The magnetic sensor 20 in its first configuration is the first MAGFET 11. A source current I.sub.S is used to bias the magnetic sensor 20 forming the first MAGFET 11. A first drain current I.sub.D1 circulates in the first drain A and a second drain current I.sub.D2 circulates in the second drain B of the magnetic sensor 20 forming the first MAGFET 11.
[0078] FIG. 9b illustrates a second configuration of the magnetic sensor 20, wherein the first angle-contact A and the fourth angle-contact D are connected together to form a source, the second angle-contact B is a first drain and the third angle-contact C is a second drain. The magnetic sensor 20 in its second configuration is a second MAGFET 12. A source current I.sub.S is used to bias the magnetic sensor 20 forming the second MAGFET 12. A first drain current I.sub.D1 circulates in the first drain B and a second drain current I.sub.D2 circulates in the second drain C of the magnetic sensor 20 forming the second MAGFET 12.
[0079] FIG. 9c illustrates a third configuration of the magnetic sensor 20, wherein the second angle-contact B and the third angle-contact C are connected together to form a source, the fourth angle-contact D is a first drain and the first angle-contact A is a second drain. The magnetic sensor 20 in its third configuration is a third MAGFET 13. A source current I.sub.S is used to bias the magnetic sensor 20 forming the third MAGFET 13. A first drain current I.sub.D1 circulates in the first drain D and a second drain current I.sub.D2 circulates in the second drain A of the magnetic sensor 20 forming the third MAGFET 13.
[0080] FIG. 9d illustrates a fourth configuration of the magnetic sensor 20, wherein the first angle-contact A and the second angle-contact B are connected together to form a source, the third angle-contact C is a first drain and the fourth angle-contact D is a second drain. The magnetic sensor 20 in its fourth configuration is a fourth MAGFET 14. A source current I.sub.S is used to bias the magnetic sensor 20 forming the fourth MAGFET 14. A first drain current I.sub.D1 circulates in the first drain C and a second drain current I.sub.D2 circulates in the second drain D of the magnetic sensor 20 forming the fourth MAGFET 14.
[0081] The magnetic sensor 20 comprising four MAGFET configurations is preferentially used in a magnetic operational amplifier according to an embodiment of the invention, instead of a single classical MAGFET. Indeed the symmetrical shape of the magnetic sensor 20 allows applying a spinning-current technique in order to remove the offset and low-frequency noise of the magnetic sensor 20. FIG. 10 shows the differential stage 1 of a magnetic amplifier MOP comprising the magnetic sensor 20, wherein the differential signal conditioner further comprises a spinning-current module 159 that periodically alternates the first, second, third and fourth configurations of the magnetic sensor 20. FIG. 10 shows a particular embodiment where each MAGFET configuration of the magnetic sensor 20 is an n-type MAGFET configuration and the differential input pair 153 is an n-type differential input pair; connections are thus similar to those of FIG. 5a. Other embodiments, not shown, are possible, where: [0082] each MAGFET configuration of the magnetic sensor 20 is an n-type MAGFET configuration and the differential input pair 153 is a p-type differential input pair; connections are then similar to those of FIG. 5b, or [0083] each MAGFET configuration of the magnetic sensor 20 is a p-type MAGFET configuration and the differential input pair 153 is a p-type differential input pair; connections are then similar to those of FIG. 5c, or [0084] each MAGFET configuration of the magnetic sensor 20 is a p-type MAGFET configuration and the differential input pair 153 is a n-type differential input pair; connections are then similar to those of FIG. 5d.
