Is common mode voltage only depends on resistor mismatch in differential amplifier?

More Biswajit Singh's questions See All

Due to channel length modulation current in mosfet increases but is this current less than triode region current?

As MOSFET current depends on the channel length and due to channel length modulation drain current increases . What will be the impact on the device?

06 July 2018 6,037 5 View

Why opamp integrator circuit is not affected by miller capacitance?

If we see the input impedance( Zi )seen looking into the inverting input node of the circuit shows its frequency independent(according to Bode Plot)? how is that possible?

05 June 2017 2,965 18 View

What happens to the operating freq of the design if system is operated high voltages?

and also What happens to the operating freq of the design if system is operated at dessert and snow places?how it affects the system operation?

04 May 2017 2,549 3 View

Why leakage current is a major problem at low voltages?

04 May 2017 220 0 View

Which topology used in low latency adc architecture?

can anybody clarify what is the difference between latency and settling time for any Analog to Digital converter.

31 December 2016 7,890 1 View

What is the Internal behaivor of BJT in saturation??

I'am trying to understand to internal behaivor of BJT when it's in saturation. why the current Ic is highets in saturation?

07 August 2016 4,727 1 View

How stability is related to bandwidth?

what is the reason if bandwidth increases then stability increases and if bandwidth decreases then stability decreases? how transient response is dependent on the bandwidth?

02 March 2016 1,745 13 View

If the gain of open loop system is doubled the gain margin of the system is

1.not affected 2.doubled 3.halved 4.one fourth of original value

06 July 2015 8,660 0 View

Why Vce(sat)=0.2V?

what will happen if resistor is connected in between emitter and ground

06 July 2015 1,445 5 View

Why fet is better chopper than bjt?

what are the reason?

06 July 2015 1,606 0 View

Binary Logistic Generalized Linear Mixed model in SPSS. Is it doable?

I want to analyses the proportion of swimming sperm of three species of fish in two salinities. To analyse the proportion of swimming sperm in a Generalized Linear Model, I would use a Binary...

03 March 2021 2,297 3 View

What is the most Operating System (OS) which can be INSTALL on Tiny hard devices like Raspberry Pi (RPi) hardware ?

I'm targeting to deploy a mesh network and manually configure MANET routing protocols. I'm preparing scenarios, architectures, and hard devices needed to do that. Are there some step-by-step...

03 March 2021 1,931 5 View

Can we classify HV and LV lines based on line length?

I have dataset which shows the length of power lines. I need to classify the lines based on the line length. Is there a rule to classify the High voltage (HV) and low voltage (LV) lines based on...

03 March 2021 4,116 4 View

How to increase a model accuracy ?

dear community, my model is based feature extraction from non stationary signals using discrete Wavelet Transform and then using statistical features then machine learning classifiers in order to...

03 March 2021 6,994 5 View

Waters 2707 HPLC autosampler problem?

I am using a 2707 waters HPLC device. When I try to inject a sample, it says missing plate or rack. I changed the needle and calibrated its position but I still get the same problem. I even get...

02 March 2021 1,408 1 View

12% ledeburitic cold work tool steel, etched for revealing retained austenite, any help for clarifying?

Hello everyone. Given microstructure image belongs to a 12% ledeburitic cold work tool steel (annealed and tempered). The sample was etched with picral (100 mL ethanol and 4 g picric acid). I...

02 March 2021 4,119 3 View

Is There Any Feasible Method To Test Fluorescent Compounds Other Than Fluorescence Spectrometers ??

Is There Any Feasible Method To Test The Efficiency Of Fluorescent Compounds Other Than UV Spectrometers ? Suggestions Would Be Appreciated !

02 March 2021 5,785 3 View

What analysis to choose with a large neste dataset and clearly skewed or kurtotic distributions?

Hello! I have a dataset of n=3000 nested within 8 countries with approximately 200 or 400 responses in each country. I originally planned to perform multilevel modelling with 4 dependent variables...

02 March 2021 6,865 1 View

How to calculate BREQ 3 questionnaire?

how to calculate BEHAVIOURAL REGULATION IN EXERCISE QUESTIONNAIRE BREQ 3 ,which contain 24 questions and each question has 5 answers (0- Strongly disagree , 1-disagree, 2- Neither agree nor...

02 March 2021 811 3 View

I am interested in medicinal chemistry field, which books are highly recommended to learn from?

I am at the beginner level in drug design and drug discovery, and I am interested to learn more about this field. Which books are highly recommended to start from and gives me all essential...

02 March 2021 8,437 2 View

U. Dreher

My guess: INA denominates one of these ex-BurrBrown, now TI INstrumentation Amplifiers. Those are named INAxxx.

DC common mode rejection depends mostly on resistor match, but only mostly. Any violation of perfect symmetrie reduces common mode rejection, including differences in the individual transistors.

AC common mode rejection in addition depends on differences in (stray) capacitances and inductances as well. (These result in phase differences between the 2 signal paths.)

I dug up 2 documents considering this topic:

http://www.analog.com/en/analog-dialogue/articles/measuring-small-differential-voltages.html

https://www.ti.com/seclit/sl/slyc124/slyc124.pdf

Both documents are just "teasers". These sites have much more to offer on this topic - and on a plethora of similar topics.

Abdelhalim Zekry

Adding to the respected colleague Dreher, instrumentation amplifiers are characterized by very high common mode rejection ratio. If the differential gain is known, then you can calculate the common mode gain as the cmrr= Ad/Ac, the differential gain to the common mode gain. Since the output voltage Vo= Ad Vd + Ac Vc ,where Vd is the differential input and Vc is the common mode input you can estimate the allowed Vc for certain tolerate error in the measurement.

As for the common mode gain suppression it is normally accomplished by using emitter tailed with nearly ideal current sources which renders the bias current of the amplifier nearly independent of the common mode gain.

The common mode gain = about RC/RE where RC is the collector resistance of the differential pair and RE is the common emitter resistance.

As for the equivalent input offset voltage it is caused by the mismatch in the input differential amplifier. It can be compensated internally by the design or externally for finished devices. Instrumentation amplifiers are designed for low input offset voltage. However it could be compensated externally.

For AC applications the effect of the the input offset voltage is less pronounced than in the DC applications. If the frequency is high enough you can overlook the input offset voltage especially when reducing the gain of the amplifier by negative feedback which is normally the case.

Best wishes