Describe common-mode rejection ratio, Electrical Engineering

Assignment Help:

Q. Describe Common-Mode Rejection Ratio ?

When there is a common-mode input voltage, i.e., when the input signals are equal and greater than zero, the output voltage of an ideal op amp is zero because vd is equal to zero. In general, the common-mode input vC is defined as vp + vn/ 2; and the difference signal vd = vp -vn is to be amplified. Common-mode gain AC is defined as the ratio vo/vC when vd = 0. The common-mode rejection ratio (CMRR) is defined by A/AC, but is usually expressed in units of decibel (dB),

1486_Describe Common-Mode Rejection Ratio.png

It is typically 90 dB, i.e., A/AC ∼ = 32,000. The ideal op amp, however, has infinite CMRR. To explain further, an op amp can be considered a special type of differential amplifier. The object of a differential amplifier, which is formally presented a little later, is to amplify "differences" in voltage between the two inputs, and to be unresponsive to voltage changes that appear simultaneously on both inputs. The differential-mode input signal is the difference between vp and vn; that is to say, vd = vp - vn. The common-mode input signal is the average value of the two input signals; that is to say, vc = (v1 + v2)/2. The output voltage of the amplifier vo is given by vo = vdAd + vcAc, where Ad (called simply A previously) is the differential-mode voltage gain and Ac is the common-mode voltage gain. Under ideal conditions, Ac is equal to zero and the differential amplifier completely rejects the common-mode signals. The departure from this ideal condition is a figure of merit for a differential amplifier and is measured by CMRR, which is the ratio of Ad to Ac. CMRR can thus be seen as a measure of an amplifier's ability to distinguish between differential-mode and common-mode signals. One of the practical advantages of a differential amplifier is its rejection of unwanted signals or noise.


Related Discussions:- Describe common-mode rejection ratio

Use kcl and kvl to determine current, For the circuit shown in Figure, use ...

For the circuit shown in Figure, use KCL and KVL to determine i 1 , i 2 , v bd and v x . Also, find v eb .

Can you explain octal to binary conversion, Q. Can you explain Octal to Bin...

Q. Can you explain Octal to Binary Conversion? It is also simple to convert from an integer octal number to binary. This is completed by: Convert the decimal number

Expression for the real power transfer capacity, Q. Consider a lossless tra...

Q. Consider a lossless transmission line with only a series reactance X. (a) Find an expression for the real power transfer capacity of the transmission system. (b) What is P

Find the magnetic-field force exerted on the moving bar, Consider the arran...

Consider the arrangement shown in Figure. A conductor bar of length l is free to move along a pair of conducting rails. The bar is driven by an external force at a constant velocit

Function generator, explain the waorking principle of function generator

explain the waorking principle of function generator

Mobile and wirelss communicatio, In a CDMA system, the signal is spr...

In a CDMA system, the signal is spread over a large bandwidth by multiplying the transmitted symbol by a sequence of short pulses, also called chips. The

Find the quantum levels, A uniform quantizer is said to have 16 levels, and...

A uniform quantizer is said to have 16 levels, and hence is called a midriser. The saturation levels are to correspond to extreme values of the message of 1 V ≤  f(t) ≤ 17 V. Find

Differentiate between heat transfer and thermodynamics, Briefly Explain ...

Briefly Explain i. Importance of thermal diffusivity. ii. Describe the laws governing Heat Transfer. iii. Differentiate between Heat Transfer and Thermodynamics iv. Des

Matlab, fast decoupled program

fast decoupled program

The operation of colpitts oscillator, Q. Explain with the help of a circuit...

Q. Explain with the help of a circuit diagram,the operation of COLPITTS OSCILLATOR. Oscillator is a circuit used to generate a.c voltage without a.c.input signal.The energy to

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd