Patent ID: 6462619
Filing Date: 2002-10-08
Classification: H03F

Abstract:
A differential input stage of an operational amplifier configured for providing a constant transconductance independent of a common-mode input voltage, said differential input stage comprising:a positive input terminal; a negative input terminal; an input stage coupled to said positive input terminal and said negative input terminal; a current source for providing a first current supply to said input stage; a current transfer circuit coupled to said current source for providing a second current supply; a proportional input stage coupled to said positive input terminal and said negative input terminal; a proportional current source coupled to said proportional input stage for providing a current proportional to said first current supply; a proportional current transfer circuit coupled to said proportional current source for providing a current proportional to said second current supply; a minimum selector circuit configured to select a minimum current; wherein said differential input stage is configured to provide a reduced transconductance by subtracting said minimum current from said second current supply.