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

Pop psw instruction , POP PSW Instruction It is similar to  above pop...

POP PSW Instruction It is similar to  above pop  instruction but instead of normal  register  pairs it uses PSW  as its operand. Program status word  comprises of the content

Find the turns ratio, Q A60-Hz, 100-kVA, 2400/240-V(rms) transformer is use...

Q A60-Hz, 100-kVA, 2400/240-V(rms) transformer is used as a step-down transformer from a transmission line to a distribution system. Consider the transformer to be ideal. (a) Fi

Electricity and gas hazards, Electricity beyond doubt is very useful and es...

Electricity beyond doubt is very useful and essential for us; but if dealt with carelessly, it can prove to be very fatal. It is compulsory for a laboratory assistant to be sure of

Determine the node voltage, Determine the node voltage: Determine the ...

Determine the node voltage: Determine the node voltage V and then current flowing through each element by using KCL. Solution Apply KCL at the node whose voltage is V.

Comparison between motorola processors and intel processors, Differentiate ...

Differentiate between Motorola processors and INTEL processors. Comparison between Motorola processors and INTEL processors: AMD/Intel processors are actually about similar t

Electron, Electron congratulations

Electron congratulations

The octal inverter 74ls 240, The  Octal Inverter 74LS 240 It is  simil...

The  Octal Inverter 74LS 240 It is  similar  to above  octal  buffer  but with  inverter output. The  logic  diagram is  shown  in figure below . Normal 0

Financing the power sector projects, Financing the power sector projects: ...

Financing the power sector projects:   Massive investment is required for the targeted expansion of the sector. It has been estimated at Rs. 9 lakh crores in the further 10 yea

Theft or pilferage of power by the existing customers, Theft or Pilferage o...

Theft or Pilferage of Power by the Existing Customers Power theft through the existing consumers is the predominant cause of loss of revenue to the electrical utilities. Almos

Back emf, Transistor Switching Circuit Design a) Sketchy a schematic d...

Transistor Switching Circuit Design a) Sketchy a schematic diagram showing how a transistor can be used to control the operation of a relay b) Determine what is meant by ba

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