Patent ID: 6400225
Filing Date: 2002-06-04
Classification: G01R,H03F

Abstract:
A differential difference amplifier for amplifying an input signal close to a negative supply voltage and adding an offset voltage to the amplified input signal, said differential difference amplifier comprising:a first non-inverting input terminal capable of being coupled to said input signal; a first inverting input terminal capable of being coupled to said negative supply voltage; a second inverting input terminal capable of being coupled to a feedback resistor coupled to an output of said differential difference amplifier; a second non-inverting input terminal capable of being coupled to said offset voltage; a first differential transistor pair comprising a first transistor having a gate coupled to said first non-inverting input and a second transistor having a gate coupled to said first inverting input; a second differential transistor pair comprising a third transistor having a gate coupled to said second non-inverting input and fourth transistor having a gate coupled to said second inverting input; a first cascode transistor pair comprising a fifth transistor having a gate coupled to said first non-inverting input and a source coupled to a drain of said first transistor and a sixth transistor having a gate coupled to said first inverting input and a source coupled to a drain of said second transistor; and a second cascode transistor pair comprising a seventh transistor having a gate coupled to said second non-inverting input and a source coupled to a drain of said third transistor and an eighth transistor having a gate coupled to said second inverting input and a source coupled to a drain of said fourth transistor.