Invention Grant
- Patent Title: Method and apparatus for an active negative-capacitor circuit to cancel the input capacitance of comparators
- Patent Title (中): 用于消除比较器的输入电容的有源负电容电路的方法和装置
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Application No.: US13602216Application Date: 2012-09-03
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Publication No.: US09124279B2Publication Date: 2015-09-01
- Inventor: Dai Dai
- Applicant: Dai Dai
- Applicant Address: US CA Carlsbad
- Assignee: Tensorcom, Inc.
- Current Assignee: Tensorcom, Inc.
- Current Assignee Address: US CA Carlsbad
- Agency: Tyrean Patent Prosecution Law Firm
- Agent Thaddeus Gabara
- Main IPC: H03H11/46
- IPC: H03H11/46 ; H03F3/45 ; H03M1/00 ; H03K5/24 ; H03M1/08 ; H03M1/18 ; H03H11/48

Abstract:
The differential output of a Programmable Gain Amplifier (PGA) is loaded by the input differential gate capacitance of a plurality of Analog to Digital converters (ADC) comparators and the differential metal layer traces to interconnect these comparators to the PGA. The differential capacitive load presented to the PGA is quite large and reduces the bandwidth of this interconnect between the PGA and ADC. To overcome the performance degradation due to the differential capacitive load, an active negative-capacitor circuit cancels the effect of the large input capacitance of the ADC comparators. This cancellation extends the gain characteristics of the interconnect between the PGA's output and the inputs of the first stage of the comparators. The active negative-capacitance is comprised of a cross pair NMOS with a capacitor connecting their sources where each NMOS is biased by a current source.
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