Patent ID: 8626098

Claim:
A transconductance comparator comprising: a comparator having an output of a detector configured to sense an amplitude of an output of a Variable Gain Amplifier (VGA) of a receiver as a first input and a reference amplitude level as a second input thereto, the comparator being configured to generate an error signal based on the first input and the second input; and a transconductance amplifier configured to have a differential voltage input based on the error signal generated through the comparator and to generate an output current, the transconductance amplifier comprising: a first current source associated with a programmable lower current limit of the transconductance amplifier; a second current source associated with a programmable upper current limit of the transconductance amplifier; a first differential pair coupled to the first current source and configured to have a first voltage of the differential voltage input applied to gate terminals of transistors thereof; and a second differential pair coupled to the second current source and configured to have a second voltage of the differential voltage input applied to gate terminals of transistors thereof, wherein at least one of: the transistors of the first differential pair and the transistors of the second differential pair are implemented with a size mismatch therebetween to eliminate an offset error in the transconductance amplifier due to a mismatch between the programmable lower current limit and the programmable upper current limit, the elimination of the offset error enabling programmability of an attack time and a decay time during automatic gain control of the VGA over a wide range of the programmable current limits of the transconductance amplifier.