Comparator with sensitivity control
AssigneeTexas Instruments Deutschland GmbH
InventorRuediger Ganz
Life of this patent
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Abstract
A comparator has a differential input stage, a current source coupled to the differential input stage for providing a tail current to one side of the differential input stage, and a differential load coupled to the differential pair and having at least one diode coupled load transistor per differential side. A load current through either one of the at least one diode coupled load transistor on either differential side is mirrored with a current mirror configuration to provide a current be fed to a respective node, each node being coupled to a respective variable biasing current source and a respective other side of the differential input stage, so as to provide a variable positive feedback to the differential input stage.
Claims13
A comparator for demodulating an amplitude modulated RF signal received in an RFID transponder, the comparator comprising:
- a differential input stage (MN1, MN2),
- a current source (Iscr) coupled to the differential input stage (MN1, MN2) for providing a tail current (I9) to the differential input stage (MN1, MN2), and
- a differential load coupled to the differential pair and comprising at least one diode coupled load transistor (MP3, MP4) per differential side, wherein
- a load current (I3, I4) through either one of the at least one diode coupled load transistor (MP3, MP4) on either differential side is mirrored out with a current mirror configuration having a factor A to provide a current (I6, I7) be fed to a respective node (N1, N2), each node (N1, N2) being coupled to a respective variable biasing current source and a respective other side of the differential input stage (MN1, MN2), so as to provide a variable positive feedback to the differential input stage (MN1, MN2).
A RFID transponder comprising:
- an antenna;
- a demodulator comprising:
- a differential input stage having a differential load having at least one diode coupled transistor coupled to a differential pair of transistors, a load current through either one of the at least one diode coupled transistor being mirrored by a current mirror having a current ration of 1:A to provide current to a respective node, each node being coupled to a respective variable biasing current source and a respective other side of the differential input stage, whereby a variable positive feedback to the differential input stage is provided.
A comparator for demodulating an amplitude modulated RF signal received in an RFID transponder, the comparator comprising:
- a differential input stage (MN1, MN2),
- a current source (Iscr) coupled to the differential input stage (MN1, MN2) for providing a tail current (I9) to the differential input stage (MN1, MN2);
- and
- a differential load coupled to the differential pair and comprising at least one diode coupled load transistor (MP3, MP4) per differential side, wherein
- a load current (I3, I4) through either one of the at least one diode coupled load transistor (MP3, MP4) on either differential side is mirrored with a current mirror configuration having a factor A to provide a current (I6, I7) be fed to a respective node (N1, N2), each node (N1, N2) being coupled to a respective variable biasing current source and a respective other side of the differential input stage (MN1, MN2), so as to provide a variable positive feedback to the differential input stage (MN1, MN2);
- wherein the variable biasing current source comprises two transistors (MN8, MN9) having their gates coupled together for being commonly controlled by a control voltage (Bias_Icntl);
- and the current mirror configuration is established by coupling two transistors (MP6, MP7) with their gates to the gates of the diode coupled load transistors.
Dependencies are inferred from the claim text.