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Common Mode Rejection Ratio (CMRR) is a measure of the ability of an electronic circuit, such as an amplifier, to reject noise and interference that is common to both the input signals. It is particularly important in differential amplifier configurations.
The calculator uses the formula:
Where:
Explanation: This formula calculates the common-mode rejection ratio for MOS with current-mirror load when resistance at drains are equal, taking into account the transconductance and resistances in the circuit.
Details: CMRR is crucial in differential amplifier design as it indicates how well the amplifier can reject common-mode signals while amplifying differential signals. Higher CMRR values indicate better noise rejection capabilities.
Tips: Enter transconductance in Siemens, finite output resistance in Ohms, and source resistance in Ohms. All values must be positive numbers.
Q1: What is a good CMRR value?
A: Higher CMRR values are better. Typically, values above 80-100 dB are considered good for most applications.
Q2: How does transconductance affect CMRR?
A: Higher transconductance generally leads to higher CMRR, as it increases the amplifier's ability to amplify differential signals while rejecting common-mode signals.
Q3: What is the role of source resistance in CMRR?
A: Source resistance helps in current limiting and affects the overall gain and CMRR of the amplifier circuit.
Q4: When is this specific formula applicable?
A: This formula is specifically for MOS with current-mirror load configurations where the resistance at drains are equal.
Q5: How can CMRR be improved in practical circuits?
A: CMRR can be improved by using matched components, increasing circuit symmetry, and using higher quality differential amplifiers.