electrown.com Power supply rejection ratio (PSRR) measures an amplifier's ability to suppress variations in its power supply voltage, ensuring stable output despite fluctuations, while common-mode rejection ratio (CMRR) quantifies how effectively it rejects input signals common to both inputs, improving differential signal accuracy. Understanding the differences between PSRR and CMRR is crucial for optimizing your circuit's performance; explore the rest of the article to learn how these parameters impact your system design.
Table of Comparison
| Parameter | Power Supply Rejection Ratio (PSRR) | Common-Mode Rejection Ratio (CMRR) |
|---|---|---|
| Definition | Ability of a device to suppress power supply variations in its output. | Ability to reject common-mode signals at the input. |
| Unit | Decibels (dB) | Decibels (dB) |
| Measured As | Ratio of change in power supply voltage to the corresponding output voltage change. | Ratio of differential gain to common-mode gain. |
| Typical Application | Power supply noise rejection in amplifiers, regulators. | Noise rejection in differential amplifiers, instrumentation amplifiers. |
| Importance | Ensures output stability against supply voltage fluctuations. | Ensures accurate differential signal measurement by rejecting noise. |
| Frequency Dependence | Varies with power supply ripple frequency. | Varies with differential input signal frequency. |
Introduction to PSRR and CMRR
Power Supply Rejection Ratio (PSRR) measures an amplifier's ability to suppress fluctuations in its power supply voltage, ensuring stable output despite supply noise. Common-Mode Rejection Ratio (CMRR) evaluates the amplifier's capability to reject input signals common to both input terminals, enhancing differential signal accuracy. Understanding PSRR and CMRR helps optimize Your circuit's performance by minimizing noise and interference from power supply variations and common-mode signals.
Defining Power Supply Rejection Ratio (PSRR)
Power Supply Rejection Ratio (PSRR) quantifies an amplifier's ability to suppress variations in its power supply voltage from affecting the output signal, ensuring stable performance despite fluctuations. Measured in decibels (dB), higher PSRR values indicate greater immunity to noise or ripple present on the power supply rails. Understanding PSRR helps you design circuits with improved noise resilience, especially when comparing it to Common-Mode Rejection Ratio (CMRR), which focuses on rejecting input common-mode signals instead of power supply variations.
Understanding Common-Mode Rejection Ratio (CMRR)
Common-Mode Rejection Ratio (CMRR) quantifies an amplifier's ability to reject input signals common to both input terminals, preserving signal integrity by minimizing noise and interference. Higher CMRR values indicate superior performance in differentiating differential signals from common-mode signals, critical in sensor and measurement applications. Unlike Power Supply Rejection Ratio (PSRR), which measures an amplifier's immunity to supply voltage variations, CMRR specifically targets elimination of unwanted noise appearing simultaneously on both inputs.
Significance of PSRR in Circuit Performance
Power supply rejection ratio (PSRR) measures an amplifier's ability to suppress power supply noise, directly impacting circuit stability and signal integrity. Common-mode rejection ratio (CMRR) evaluates the rejection of input signals common to both inputs, influencing noise immunity from interference. Your circuit's performance heavily depends on high PSRR to ensure consistent operation despite fluctuations in power supply voltage.
The Role of CMRR in Operational Amplifiers
Common-Mode Rejection Ratio (CMRR) measures an operational amplifier's ability to reject input signals common to both input terminals, directly impacting its precision in differential signal amplification. High CMRR ensures minimal interference from noise or unwanted signals present simultaneously on both inputs, making it critical for accurate measurement and signal processing applications. Unlike Power Supply Rejection Ratio (PSRR), which focuses on supply voltage variations, CMRR specifically enhances the amplifier's stability against common-mode noise.
Key Differences Between PSRR and CMRR
Power Supply Rejection Ratio (PSRR) measures an amplifier's ability to suppress variations in its power supply voltage from affecting the output signal, while Common-Mode Rejection Ratio (CMRR) quantifies the ability to reject common-mode signals present simultaneously on both differential inputs. PSRR is crucial for maintaining signal integrity in noisy power environments, whereas CMRR is vital for eliminating noise or interference common to both input lines, such as electromagnetic interference. Your choice between prioritizing PSRR or CMRR depends on whether power supply noise or input signal noise poses a greater threat to overall system performance.
Measurement Techniques for PSRR and CMRR
Power supply rejection ratio (PSRR) and common-mode rejection ratio (CMRR) are measured using specialized test setups involving signal analyzers and precision sources to isolate the relevant interference signals. PSRR measurement involves applying a varying power supply voltage ripple and observing its impact on the output signal, often conducted with a low-noise function generator and spectrum analyzer to quantify output changes relative to power variations. CMRR is typically evaluated by applying a common-mode input voltage while measuring the differential output response, using differential probes and instrumentation amplifiers to determine the ratio of differential gain to common-mode gain accurately.
Factors Affecting PSRR and CMRR Values
Power supply rejection ratio (PSRR) and common-mode rejection ratio (CMRR) are influenced by circuit topology, device matching, and frequency variations. Variations in power supply noise, transistor mismatches, and parasitic capacitances degrade PSRR, while input stage design, resistor matching, and common-mode input voltage range impact CMRR. Temperature changes and process variability also affect both PSRR and CMRR performance in precision amplifiers.
Improving PSRR and CMRR in Electronic Design
Improving Power Supply Rejection Ratio (PSRR) and Common-Mode Rejection Ratio (CMRR) in electronic design involves optimizing circuit topology to minimize noise coupling from power sources and common-mode signals. Techniques such as using low-noise voltage regulators, proper grounding, and differential amplifier configurations enhance PSRR and CMRR performance. Your design benefits from careful component selection and layout strategies that reduce interference, ensuring signal integrity and overall system stability.
Practical Applications: Choosing Between PSRR and CMRR
Power supply rejection ratio (PSRR) is crucial in applications where maintaining signal integrity from power supply fluctuations is essential, such as in audio amplifiers or precision analog circuits. Common-mode rejection ratio (CMRR) is more significant in environments with high common-mode noise, like sensor interfaces or differential signal processing, where your goal is to minimize interference from external noise sources. Choosing between PSRR and CMRR depends on whether your primary concern is power supply noise or common-mode noise affecting your device's performance.
Power supply rejection ratio vs common-mode rejection ratio Infographic
