Fast start up control circuit

A chopper amplifier circuit, comprising:

• an operational amplifier circuit having an inverting input, a noninverting input and an output;
• a notch filter circuit configured to be operated by a chopping pulse, the notch filter circuit comprising:
• an input connected to the output of the operational amplifier circuit;
• a first branch having a first plurality of switches and a first capacitor;
• a second branch having a second plurality of switches and a second capacitor;
• and
• an output connected as a feedback signal to the inverting input of the operational amplifier circuit;
• a chopping delay switch connected to selectively short-circuit a portion of the first branch and a portion of the second branch to each other;
• and
• a control circuit connected to the operational amplifier circuit and the chopping delay switch, the control circuit configured to:
• detect establishment of the feedback signal at the operational amplifier circuit;
• close the chopping delay switch to short-circuit the portion of the first branch and the portion of the second branch, prior to detecting the establishment of the feedback signal at the operational amplifier circuit;
• and
• open the chopping delay switch, responsive to the detecting the establishment of the feedback signal at the operational amplifier circuit.

A method comprising:

• receiving a noninverting input to a chopper amplifier circuit, the chopper amplifier circuit comprising an operational amplifier and a notch filter that is in series connection with the operational amplifier and has an output of the notch filter connected as a feedback signal to an inverting input of the operational amplifier, wherein a chopping delay switch is in a closed state to short-circuit a first branch of the notch filter having a first capacitor and a second branch of the notch filter having a second capacitor, to each other;
• determining establishment of the feedback signal at the operational amplifier, according to a control circuit connected to the operational amplifier;
• generating a delay to opening the chopping delay switch, based on the determining the establishment of the feedback signal at the operational amplifier;
• and
• changing the chopping delay switch to an open state, based on the determining the establishment of the feedback signal at the operational amplifier and the delay.