Define power-supply rejection ratio (PSRR) and how it affects circuit performance.

Define power-supply rejection ratio (PSRR) and how it affects circuit performance.

• A. PSRR quantifies how supply voltage variations affect the output; better PSRR means less output variation due to supply ripple; typically expressed in dB.
• B. PSRR is the ratio of input resistance to output resistance.
• C. PSRR stands for Power Supply Regulator Ratio.
• D. PSRR measures phase shift of the output.

Answer: (A)

Power-supply rejection ratio measures how much the output moves when the supply voltage changes. A circuit with good PSRR keeps its output stable despite ripple or noise on the power rails. It is usually given in decibels, reflecting how effectively supply variations are attenuated at the output. In practice, higher PSRR means smaller output variation for a given amount of supply ripple, which is crucial for precision amplifiers and ADC front-ends where you don’t want supply noise to masquerade as signal. A concrete way to think about it is that if a supply ripple of ΔVs causes an output change of ΔVout, the PSRR in dB is 20 log10(ΔVs/ΔVout); larger values indicate stronger rejection. The other choices don’t describe this relationship: they refer to a resistance ratio, a non-existent expansion of the acronym, or a phase-measurement property, none of which capture how supply variations affect the output.

Power-supply rejection ratio measures how much the output moves when the supply voltage changes. A circuit with good PSRR keeps its output stable despite ripple or noise on the power rails. It is usually given in decibels, reflecting how effectively supply variations are attenuated at the output. In practice, higher PSRR means smaller output variation for a given amount of supply ripple, which is crucial for precision amplifiers and ADC front-ends where you don’t want supply noise to masquerade as signal. A concrete way to think about it is that if a supply ripple of ΔVs causes an output change of ΔVout, the PSRR in dB is 20 log10(ΔVs/ΔVout); larger values indicate stronger rejection. The other choices don’t describe this relationship: they refer to a resistance ratio, a non-existent expansion of the acronym, or a phase-measurement property, none of which capture how supply variations affect the output.