= Electrical noise reduction
Improve a circuit's <signal-to-noise ratio> by reducing unwanted coupling and physical noise sources while retaining the signal bandwidth. Important methods include lowering appropriate resistances or temperature to reduce <thermal electrical noise>, controlling leakage and bias currents relevant to <shot noise>, minimizing pickup with shielding and small loop area, and selecting an <operational amplifier> for the source <electrical impedance>. Filtering limits integrated <noise> only if it preserves the information-bearing spectrum; a <lock-in amplifier> can move detection above a <flicker noise> region and select a narrow band. Uncorrelated noise <variances> add, whereas coherent pickup requires its phases and correlations to be considered. Repeated averaging reduces independent random error, but does not remove an arbitrary <systematic error> or slow drift.
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