Patent ID: 7868690

Claim:
A comparator for demodulating an amplitude modulated RF signal received in an RFID transponder, the comparator comprising: a differential input stage (MN 1 , MN 2 ), a current source (Iscr) coupled to the differential input stage (MN 1 , MN 2 ) for providing a tail current (I 9 ) to the differential input stage (MN 1 , MN 2 ), and a differential load coupled to the differential input stage and comprising at least one diode coupled load transistor (MP 3 , MP 4 ) per differential side, wherein a load current (I 3 , I 4 ) through either one of the at least one diode coupled load transistor (MP 3 , MP 4 ) on either differential side is mirrored out with a current mirror configuration having a factor A to provide a current (I 6 , I 7 ) be fed to a respective node (N 1 , N 2 ), each node (N 1 , N 2 ) being coupled to a respective variable biasing current source and a respective other side of the differential input stage (MN 1 , MN 2 ), so as to provide a variable positive feedback to the differential input stage (MN 1 , MN 2 ).