Operational amplifier integrator

摘要

An integrator circuit comprises an operational amplifier which has a transistor stage ( 1 ) with an input terminal ( 4 ) and an output terminal ( 3 ), a feedback capacitor ( 2 ) connected between the input terminal ( 4 ) and the output terminal ( 3 ), and a resistor ( 5 ) connected to the input terminal ( 4 ), and also has an additional circuit branch ( 20 ) comprising a second capacitor ( 22 ) and a second resistor ( 25 ) connected in series one with the other and connected between the output terminal ( 3 ) of the transistor stage ( 1 ) and voltage comprising the inverted input voltage to the integrator circuit. Preferably two additional circuit branches ( 320, 320' ) are provided. One may be connected between the non-inverting or positive output terminal ( 33 ) of the transistor stage ( 1 ) and the inverting or negative input of the integrator. The other circuit may be connected between the negative output terminal ( 37 ) of the transistor stage ( 1 ) and the positive input of the integrator. This is particularly useful for balanced amplifier topology. The invention finds particular application in the first filter stage (integrator) in a sigma delta analog to digital conversion circuits and provide an improved operational amplifier integrator and particularly helps in compensating for a right halfplane zero.