US Patent 8174418 Inexpensively improving resolution and reducing noise of low-noise signals

Systems and methods for improving resolution of low-noise signals in an analog-to-digital conversion circuit. A simple, low cost pseudo-noise generating circuit is disclosed that, when connected to the signal conditioning circuitry of A/D conversion circuit, adds pseudo-noise to an analog input voltage signal. Additional pseudo-noise is beneficial for improving the resolution of analog-to-digital conversion when oversampling and summing or averaging are used in post-conversion processing operations. The circuit is composed of a plurality of resistors configured in at least two parallel branches. An individually switchable voltage source output is connected to each branch. A resulting analog voltage can be measured at a common termination point for the branches, depending on the combination of switchable voltage source output turned on, and the branch to which the voltage output is applied. By varying the combination of switchable voltage source outputs turned on over time, a known analog pseudo-noise signal is developed.