Abstract An AC amplifier system which comprises an all-stage direct coupling type AC amplifier and a negative feedback circuit connected across the all-stage direct coupling type AC amplifier which includes a DC amplifier connected to the output side of the AC amplifier and designed such that the drift and offset involved therein are extremely small compared to that of the AC amplifier, the DC amplifier having a voltage amplification degree greater than unity for a DC and super-low frequency range, the output of the DC amplifier being coupled to the input side of the AC amplifier for the negative feedback of part of the output of the AC amplifier, thereby greatly reducing the drift and offset of the AC amplifier system.
An AC amplifier system comprising an AC amplifier to amplify AC signals and a negative feedback circuit connected across said AC amplifier, said negative feedback circuit including a DC amplifier, and said DC amplifier having a cutoff frequency lower than the low cutoff frequency of said AC amplifier and being designed such that the drift and offset involved therein are extremely small compared to the drift and offset in said AC amplifier.
Claim 2
Dependent Claim
72 words
An AC amplifier system comprising an AC amplifier to amplify AC signals and a negative feedback circuit connected across said AC amplifier, said negative feedback circuit including a DC amplifier, and said DC amplifier having a cutoff frequency lower than the low cutoff frequency of said AC amplifier and being designed such that the drift and offset involved therein are extremely small compared to the drift and offset in said AC amplifier.
Claim 3
Dependent Claim
16 words
An AC amplifier system according to claim 1 wherein said DC amplifier comprises a differential amplifier.
Claim 4
Dependent Claim
16 words
An AC amplifier system according to claim 1 wherein said DC amplifier comprises a chopper amplifier.
Claim 5
Dependent Claim
28 words
An AC amplifier system according to claim 1 wherein said AC amplifier is an all-stage direct coupling type AC amplifier and said DC amplifier comprises a differential amplifier.
Claim 6
Dependent Claim
28 words
An AC amplifier system according to claim 1 wherein said AC amplifier is an all-stage direct coupling type AC amplifier and said DC amplifier comprises a chopper amplifier.
Claim 7
Dependent Claim
25 words
An AC amplifier system according to claim 1 wherein said negative feedback circuit further includes means for determining the feedback factor of said feedback circuit.