Patent ID: 7236015

Claim:
A circuit to supply a variable biasing current to a fast switching comparator, where said biasing current has its maximum when a voltage difference of said fast switching comparator's two input signals is zero, in order to achieve fast switching characteristics of said fast switching comparator, and where said biasing current is reduced at all other times, to achieve overall reduced power consumption, comprising: a current source for providing a reference current, building a key element of a reference current branch of a current mirror; said current mirror for mirroring said reference current from said reference current branch into a second current branch of said current mirror, called a biasing current branch, and resulting in a current mirror output current, which is equivalent to said reference current multiplied by a current mirroring ratio of the current mirror and which said biasing current branch of said current mirror then feeds to said fast switching comparator as said biasing current; a circuit arrangement to modify the current mirroring ratio of said current mirror, connected in series with said two branches of the current mirror and controlled by two signals operating as two ratio controlling inputs in order to modify said current mirroring ratio, then resulting in said biasing current being modified to a value, which is equivalent to said reference current multiplied by said modified current mirroring ratio; a connection circuit to connect said two fast switching comparator input signals to said two ratio controlling inputs of said circuit arrangement to modify the current mirroring ratio, which modifies the current mirroring ratio in a way so that said biasing current is reduced, when said voltage difference of said two input signals increases and that said biasing current is increased when said voltage difference of said two input signals decreases until said voltage difference of said two input signals is zero, wherein said connection circuit comprising: an alternating mechanism alternating a connection of said two input signals and said two ratio controlling inputs of said circuit arrangement to modify the current mirroring ratio; means to control said alternating mechanism to select a direction of change of said current mirroring ratio, based on a signal indicating a polarity of said voltage difference of said two input signals; and means to determine a status of a comparison of said two input signals and providing said signal indicating the polarity of said voltage difference of said two input signals to said means to control said alternating mechanism.