Power Supply Rejection Ratio

Definition

Power Supply Rejection Ratio (PSRR) is a measure of how well an operational amplifier can reject variations in its power supply voltage, indicating the degree to which the output remains stable despite fluctuations in supply voltage. A higher PSRR means that the op-amp is less affected by changes in its power supply, which is crucial for maintaining signal integrity in practical applications where power supply noise can degrade performance.

5 Must Know Facts For Your Next Test

1. PSRR is typically expressed in decibels (dB), and a value of 20 dB indicates that a change of 1V in the power supply will result in a change of 0.1V at the output.
2. In practical circuits, achieving a high PSRR can help improve overall circuit performance by minimizing the effect of noise from power supplies on the signal being processed.
3. The PSRR value can vary with frequency; generally, it decreases at higher frequencies due to the limitations of internal circuit components within the op-amp.
4. Op-amps designed for low-noise applications often feature higher PSRR specifications to ensure better performance under varying supply conditions.
5. Designers often implement bypass capacitors and other filtering techniques to enhance PSRR in circuits using op-amps.

Review Questions

• How does the Power Supply Rejection Ratio impact the performance of an operational amplifier in practical applications?
  • The Power Supply Rejection Ratio plays a critical role in ensuring that an operational amplifier performs reliably by minimizing the impact of power supply variations on its output. A higher PSRR indicates that changes in the supply voltage will have a smaller effect on the output signal, leading to improved signal integrity. This is especially important in sensitive applications where noise from the power supply can significantly distort the desired signal.
• Discuss how bypass capacitors can enhance the Power Supply Rejection Ratio in practical op-amp circuits.
  • Bypass capacitors are used in conjunction with operational amplifiers to improve their Power Supply Rejection Ratio by providing a low-impedance path for high-frequency noise present on the power supply lines. When connected close to the op-amp's power pins, these capacitors effectively filter out unwanted AC components, ensuring that only stable DC voltage reaches the op-amp. This helps maintain the stability and accuracy of the output signal by reducing fluctuations caused by noisy power supplies.
• Evaluate how variations in frequency affect Power Supply Rejection Ratio and what implications this has for circuit design.
  • Variations in frequency have a significant impact on Power Supply Rejection Ratio, as PSRR tends to decrease at higher frequencies due to internal capacitances and inductances within the operational amplifier. For circuit designers, this means that while a high PSRR may be achievable at low frequencies, additional measures such as proper layout techniques and component selection become essential when dealing with high-frequency signals. Understanding this behavior allows engineers to design more robust circuits that maintain performance across a wide range of operating conditions.

Related terms

Common-Mode Rejection Ratio: A measure of an op-amp's ability to reject common-mode signals, which are voltages that appear simultaneously and in-phase on both input terminals.

Open-Loop Gain: The gain of an operational amplifier without any feedback applied, representing the maximum amplification possible under ideal conditions.

Voltage Regulation: The ability of a power supply to maintain a constant output voltage despite variations in load current or input voltage.