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

Calculate the actual frequency response, Using the LM741operational amplifi...

Using the LM741operational amplifier build a current amplifier with the voltage gain of  |A V | = 300 v/v ± = 20% . Measure all necessary parameters of the amplifier (as per delive

What is signal multiplexing, Q. What is Signal Multiplexing? Frequency-...

Q. What is Signal Multiplexing? Frequency-division multiplexing (FDM) and time-division multiplexing (TDM) systems. When data from many sources in time are interlaced, the inte

Calculate the stator input current, Q. Calculate the stator input current? ...

Q. Calculate the stator input current? The parameters of the equivalent circuit shown in Figure for a three-phase, wye-connected, 220-V, 10-hp, 60-Hz, six-pole induction motor

Sub subtract instruction, SUB Subtract Instruction This  instruction  i...

SUB Subtract Instruction This  instruction  is used to  subtract the contents of any  register  or memory location from  the contents of  accumulator. There are two  formats as

Pareto Analysis, Pareto Analysis Pareto charts are based on the princi...

Pareto Analysis Pareto charts are based on the principle - "Vital Few Trivial Many". It allows user to focus attention on a few significant factors in a process. It is very us

Microcontroller interfacing, The conveyor system is driven by a 240 Volt 50...

The conveyor system is driven by a 240 Volt 50 Hz AC motor requiring a continuous 1 Amp supply. The conveyor has single direction operation. The loading mechanism for the winder

Diodes, Analysis of diode circuits

Analysis of diode circuits

High voltage distribution system or hvds, High Voltage Distribution System ...

High Voltage Distribution System or HVDS Adoption of HVDS (High Voltage Distribution System) through converting existing LVDS to HVDS reduces the technical losses appreciably.

Explain memory mapped i/o scheme for the allocation, Explain Memory Mapped ...

Explain Memory Mapped I/O Scheme. Memory Mapped I/O Scheme: In this scheme there is only one address space. Address space is explained as all possible addresses which microproc

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