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Power Supply Rejection Ratio (PSRR) is an important parameter in analog circuit design. It measures a circuit’s ability to suppress variations in the power supply voltage from affecting its output. A high PSRR indicates better immunity to power supply noise, which is crucial for sensitive analog applications.
What is PSRR?
PSRR is expressed in decibels (dB) and quantifies how effectively a circuit rejects fluctuations in the power supply voltage. It is especially relevant in amplifiers, voltage regulators, and other analog components where stability is essential.
Calculating PSRR
The basic formula for PSRR is:
PSRR (dB) = 20 * log10 (ΔVSupply / ΔVOutput)
Where ΔVSupply is the change in supply voltage, and ΔVOutput is the resulting change in output voltage. To determine PSRR experimentally, apply a known variation to the power supply and measure the corresponding change at the output.
Factors Affecting PSRR
Several factors influence PSRR, including circuit topology, device characteristics, and frequency. Typically, PSRR decreases at higher frequencies due to parasitic effects and device limitations.
Design techniques such as proper biasing, filtering, and layout optimization can improve PSRR. Selecting components with better noise immunity also contributes to higher rejection ratios.
Applications of PSRR
PSRR is critical in applications like audio amplifiers, radio receivers, and precision measurement systems. Ensuring high PSRR helps maintain signal integrity and reduces noise interference from power supply variations.