A practical opamp is designed to approach the characteristics of the ideal opamp as closely as possible. The open loop voltage gain of an ideal opamp is infinite, so while this is actually impossible to achieve practical opamps are built with as high an open loop voltage gain as possible.
CMRR
That way they can filter noise (assumed to be common on both input terminals) and extract the signal even if it's relatively weak.
741 opamp
An opamp buffer circuit is one where the input signal is connected to the plus input, and the output is connected to the minus input. Within the performance limitations of the opamp, the output will track the input. The advantage of the buffer circuit is that is presents very little load impedance to the input signal, while providing a low impedance from the output to drive whatever circuitry is connected there.
A high CMRR prevents the opamp from passing undesirable common mode signals.
CMRR is common mode rejection ratio. it is the ratio of Differential gain to common mode gain. CMRR=Ad/Ac
A practical opamp is designed to approach the characteristics of the ideal opamp as closely as possible. The open loop voltage gain of an ideal opamp is infinite, so while this is actually impossible to achieve practical opamps are built with as high an open loop voltage gain as possible.
CMRR
A high Common-Mode Rejection Ratio (CMRR) indicates a better ability of a circuit to reject unwanted noise or interference that is common to both input signals. This results in improved accuracy and stability of measurements or signals being processed by the circuit.
Decibel (dB) is a unit for expressing the Common-Mode Rejection Ratio (CMRR) because CMRR is typically expressed in terms of the logarithm of the ratio of the common-mode input voltage to the differential mode input voltage. Using decibels allows for easier comparison and understanding of the CMRR values, especially since CMRR values can span a wide range. It also simplifies calculations involving CMRR.
Output impedance in an op-amp is not high - it is low - input impendance is high, and this is because the input stage transistors have high gain.
Because op amp consist differential amplifier and they posses high input impedance so that op-amp also posses high input impedance.
A comparator is simply an opamp with a certain configuation of external circuitry ( a few components) that make it function as a comparator.
That way they can filter noise (assumed to be common on both input terminals) and extract the signal even if it's relatively weak.
pseudo
You want an amplifier to reject common mode signals (the same signal applied to both inputs of a differential amplifier) because:it is generally noise, which sounds like staticit can cause drift in the amplifier eventually saturating it, causing clipping distortionBTW, single ended input amplifiers by definition have a CMRR of zero.