Characteristics of Negative Feedback – Negative Feedback Amplifier – Electronic Devices and Circuits


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from Ekeeda Hello friends here we will discuss about the next topic of feedback
amplifier that is chapter number 5 that topic is characteristics of negative
feedback so as far as negative feedback is concerned there are lots of
characteristics that are hazardous sometimes and sometimes it will be very
very beneficial so contradictory part is the gain so gain is reduced by using the
negative feedback but at the same time I am getting so many beneficial quantities
so many beneficial characteristics from the negative feedback that we have to
learn in this particular video now as far as negative feedback is concerned
you all know that we are getting less gain
okay so that is the first characteristics whether it is
advantageous or disadvantageous that does not matters for me right now for
the characteristics of the negative feedback okay so we will write the
reduction of the game right as far as reduction of the gain is
concerned sometimes you feel that you why we are using that negative feedback
then right at the same time be the same gain factor I will get that D
sensitivity of the game what does the sensitivity of the gain is okay so if I
am saying that that gain factor sometimes and get Suvari right so even
if it is linear amplifier that gain factor if the output voltage is
fluctuating then the gain factor may get very right so that gain factor variation
in the open loop gain leads to have very small change in the gain at the closed
loop configuration that is beneficial for us right so even if gain
reduced that change in the game is not that much higher as compared to your
open-loop gain so change in the game is not high okay that is called as the
sensitivity okay so D sensitivity factor is important
aspect as far as negative feedback is concerned okay so here we will say that D sensitivity increases that means do
whatever change in the output voltage and get any change in the gain
perspective I am getting that is not say that mean that is not higher as compared
to your open-loop gain okay so that we will discuss in detail
about the effect of the gain on the effect of the negative feedback on the
game right so that is a different topic altogether here we will learn only the
characteristics now the second characteristic that we
will be getting is nothing but it controls the input and output resistance
so as far as amplification is concerned we all know that your ideal voltage
amplification Kelly we have to have the input resistance should be very very
high and output resistance should be very very low okay so we take one simple
example first of all we will write that it controls input and output resistance okay so it controls the input and output
resistance taekman simple example so let’s have one different page for that
let us understand I will draw two diagrams that we have already learned okay so as far as this let’s just see
are seeing are a this is a two and this is our one and I’m saying that this is
your DC reference voltage this is your ground and this is your input voltage I
am giving at the base terminal I am giving output and I am getting output at
the collector terminal now as far as input output characters or input output
resistances are concerned so if we draw the AC equivalent circuit that and that
will look like simple this will be our B that is nothing but the parallel
combination of r1 and r2 and here will be getting the our pi-1 and keep this in
mind that what if I apply the capacitance which will be at the
parallel to your r ii if i am placing parallel capacitance with re then i can
say that that are a will be redundant that means that this particular
resistance will not come into picture as far as AC equivalent model is considered
now we will do the AC equivalent model for this particular circuit and will be
getting that this is your GM VI 1 and question arises if I apply capacitor in
parallel with our e right then we will not come into picture that means there
is there is no path for the output voltage to reach at the input right
because current is passing but voltage is not passing right so I can say that
this R II if it comes into picture if capacitor is not there right then
what will be the effect on the input side resistance obviously this input
resistance will get increased so if we say that this in this RT will get
shifted towards the base side I will be getting this RB will become R by 1 plus
1 plus beta times R II so that factor this particular factor will need to
increase your input resistance right so this is how that our
is nothing but your feedback circuit and that will need to change your input
resistance right so obviously if your output resistance will also get
increased but not and that much a significant level right in this
particular circuit but obviously in another circuit it is important to have
the negative feedback to control your input as well as output resistance okay
so this example is enough I guess for the characteristics second
characteristic that is nothing but controls the input and output resistance
so let’s move towards this third part of your characteristics of a negative
feedback and the third characteristic says that it increases the bandwidth practically this is a very important
aspect as well as far as amplifier is concerned so if I’m increasing the
bandwidth I can use the longer a large range of the frequencies to work as an
amplifier right so this is beneficial characteristics as far as a negative
feedback amplifier is concerned then the fourth let’s move towards the fourth
characteristic that fourth characteristic is immunity of noise so the fourth characteristic that we have
learnt immunity of the amplifier towards the noise to noise immune to noise so I
can say that if noise is reduced then your distortion will also getting
reduced so I say that you are less Distortion or I can say that distortion
is reduced by using negative feedback okay so increased bandwidth is done
noise immunity is done then less distortion is done reduction of the gain
is done now we’ll have to learn the sixth characteristic as non-linearity it
will not affect the non-linearity so as far as non-linearity is concerned the
women learn the complete task complete mathematical expression regarding this
non-linearity bandwidth then noise then reduction with the gain D sensitivity
all these things we will learn as a separate chapter here we will just have
to learn that these are nothing but the characteristics of negative feedback so
we will stop here for this particular video within the next videos we will
learn some different aspects of the negative feedback some classification of
the negative feedback topologies and then we will learn some problem based on
the negative feedback so stay tuned for that to learn more and more NEC along
with me along with equal our videos thank you so much

One comment on “Characteristics of Negative Feedback – Negative Feedback Amplifier – Electronic Devices and Circuits”

  1. Ekeeda says:

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