Importance

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Abstract

A reference voltage circuit in an integrated circuit analog-to-digital converter includes a band gap circuit, a first field effect transistor coupling an output conductor of the band gap circuit to a first external bypass capacitor and a non-inverting input of a buffer circuit. A second field effect transistor couples the first conductor to a non-inverting input of the buffer circuit. An output of the buffer circuit is coupled to an inverting input thereof. The first and second field effect transistors are turned on during conversions, during which the first field effect transistor and the first bypass capacitor coacting to filter high frequency noise produced by the band gap circuit to apply a precise reference voltage to the non-inverting input of the buffer circuit. Between conversions, the first and second field effect transistors are turned off to isolate the first bypass capacitor and preserve its charge, so that the first bypass capacitor does not need to be charged up when the first and second field effect transistors are turned back on.

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First Claim