Joy Y. Zhang

A Micropower Chopper-Stabilized Operational Amplifier Using a SC Notch Filter With Synchronous Integration Inside the Continuous-Time Signal Path

A micropower chopper stabilized opamp is presented. The new topology incorporates a switched capacitor filter with synchronous integration inside the continuous time signal path virtually eliminating chopping noise. A three-stage amplifier with multipath nested Miller compensation is modified to incorporate chopping of the input stage, sinc filtering to notch any chopping ripple, and a compensation scheme to maintain an undistorted high-speed signal path. Characteristics of the amplifier presented include rail to rail input and output operating on supplies of 1.8 to 5.5 V over -40degC to 125degC. Quiescent supply current is 17 muA, input offset is 3 muV, input offset drift is 0.02 muV/degC, GBW is 350 kHz, and the chopping frequency is 125 kHz. Die area is 0.7 mm2 using a precision analog mixed-signal CMOS process combining low-noise 0.6-mum analog transistors with 0.3-mum digital CMOS capability

A Micropower Chopper-Stabilized Operational Amplifier using a SC Notch Filter with Synchronous Integration inside the ContinuousTime Signal Path

A micropower chopper-stabilized opamp uses an SC notch filter with synchronous integration inside the CT signal path to eliminate chopping noise. Characteristics include rail-to-rail I/O, 15muA supply current at 1.8 to 5.5V, 2muV offset, 55nV/radicHz noise, 350kHz GBW, and a chopping frequency of 125kHz. The die area is 0.7mm2 using 0.6mum CMOS