Apparatus for and method of autozeroing the output of a charge-to-voltage converter

摘要

The invention is an autozeroing circuit for use in processing low level electrical charge signals by an integrating operational amplifier. The autozeroing circuit includes a switching circuit that periodically charges and discharges the integrating capacitor of the amplifier during set and reset phases of an operation cycle so that during the set phase of the cycle the input signal is integrated and processed by processing circuitry including an A/D converter, and during the reset phase the integrator is cleared. The circuit includes a storage capacitor connected between the output of the operational amplifier of the integrator and the input to the processing circuitry, and a switch selectively operable to clamp the input of the processing circuitry to system ground during operation of the switching circuit in the amplifier so that the set phase of the cycle can begin with a known level of input (ground) at the input of the processing circuitry, independent of noise and artifacts attributed to the operation of the switching circuit in the integrator.