# Types of Coupling in Multistage Amplifier- Multistage Amplifier – Electronic Devices and Circuits

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from Ekeeda Hello Friends in this particular video we will learn the
second chapter of ADC to semester number 4 for Mumbai University branch
although it is for EXTC branch it is important for different branches such as
electrical intrumentation computers and so on so we are learning multistage
amplifier and in this particular video we will learn the types of coupling in
the multi stage amplifier so far we have discussed the multi stage amplifier
concept so that that is nothing but the improvement in the gain improvement in
the input impedance output impedance and so far so we will learn the three
categories of the coupling of multi stage amplifier so what would you mean
by the term as coupling so coupling means in which way I will connect the
output of first stage to the input of second stage output of second stage to
the input of third stage and so on so there are different ways with which we
will connect it output of first stage to input of second stage and so on okay
so there are different techniques we will be using that are nothing but first
is RC coupling second is transformer coupling and third one is direct coupling first one is RC coupling second one is
transformer coupling and third one is direct coupling so if we are looking in
this particular type will getting we’ll get to know that if you are taking RC
coupling that means resistance through resistance and capacitance capacitors we
will join the output of course stage two input of second stage and so on in the
transformer coupling we will make use of the transformer to join the output of
first stage two input of second stage and in the direct coupling obviously the
word addict tells you that the output of cost is directly connected to the input
of second stage and so on so we will learn one by one with the RC coupling
the transformer coupling and direct coupling in the different way
so first is RC coupling so I will draw the diagram then we will get to know
that how it is getting connected even though R and C is been used but the
connection orientation will be different take the live example of using let’s say
BJT as an amplifier the first stage this is input coupled so input is
coupled with the capacitor and these two shunt resistances that is nothing but r1
and r2 this is our C and this is our e okay now here we will be getting the
another capacitor that is C c2 which will act as a coupling between first
stage and the second stage so here we will say that this is the second stage I
am trying trying to draw I can say that this is resistance r1 and this is
resistance r2 or this is r3 and r4 I can say as it is combining with r1 and r2
are e2 I can say here are e1 RC 1 you can have different DC level this will be
VCC 2 this will be VCC 1 okay and again here connect the output with coupling
capacitor C C 3 right now I can have the flexibility to use c e 1 that is bypass
capacitor 1 and bypass capacitor 2 depending on the situation depending on
the requirement of the gain from the customer side we will design so here
what is different thing that we have to learn coupling is using these two
connections this capacitor is basically not directly connected to the input of
the next stage rather this capacitor along with the shunt resistance r3 and
r4 right this connection is giving the kind of coupling that is called as RC
coupling okay so in RC coupling I can say C
in series and are in shunda so you can have any configuration any biasing types
here I have drawn voltage divider more sophisticated type voltage divider
because it gives more stability than that of different biasing techniques so
R 3 R 4 and CC 2 R 3 parallel are both connection in shunt and CC 2 in series
that forms the coupling between first stage and second stage so here I can say
that this is your first stage and this is your second stage in this particular semester we’ll just
have to learn to stage amplifier but it is a possible to have multiple stage or
multistage amplifier having in four stages four or five stages four stages
but as we learn more and more stages what will happen your bandwidth will
reduce reduced and reduces and your gain will increase increase and increases so
we have to compensate with your gain as well as bandwidth so depending on the
customer requirement we’ll have to get that particular amount that particular
stages of multi stage amplifier so in this particular RC coupling what are the
advantages that we’ll be getting so advantages will write in the blue form
advantages it’s a very simple it will get very simple and this this basically
more advantage most use this RC coupling this is because we isolate two stages by
using in the DC analysis phenomena so CC two is reading opened in DC right so
basically first stage and seeing the first stage and second stage getting
isolated by using this capacitor and the resistance network that is RC coupling
okay few more advantages we have it is of cheap so cost-effective I can say right it is more cost-effective it will
require less space as far as fabrication is concerned so this was very important
as far as manufacturing is concerned less space and weight and fourth
important is it is mostly used in all your frequency range so used in a F
range the frequency response which will be getting is excellent in a fridge so
we will have to learn what are the disadvantages that will
getting in this particular RC coupling so disadvantages the disadvantages that
is it has not been used for impedance matching networks for example if we want
to connect two circuits having different impedance for example input impedance
and output impedance of course circuit alone to connect I want to connect first
circuit into second dislocate and output impedance of course that it is not
matching with the second stuff second circuit crying put impedance that I am
going to connect with the output of first then what will happen will have to
connect the another circuit which will match two impedances right so basically
this is not even used for impedance matching right so impedance matching is
not good for this particular RC coupling circuit so
not good for impedance matching whatever voltage and power gain that we’ll be
getting that is low as compared to other techniques other two techniques it’s
been used in a French we get a significant gain but if you want more
than that particular value of gain then it has not been useful okay so this jutsu our RC network we will be
getting the noise right so some noise will be there in the RC coupling so if
you take any any kind of circuit noise has to be there noise is like attention
you cannot reduce the tension you cannot you cannot completely destroy the
tension same as that of tension the noise is has to be there in the circuit
but we can reduce that noise but we cannot destroy that noise as compared to
other two networks other two types of coupling here will be getting the large
noise so okay so far we have discussed advantages
if are dominating over disadvantages then we’ll be using this RC coupling as
far as obvious a customer requirement is concerned then we will learn the other
second type of coupling that is nothing but this transformer type of coupling we
will learn that this is a simple RC network it is simple asana – no it is not as a
network it’s amplifying and I will not be using this is this not being used and
will cut this part and this is the at the output stage will be using the
transformer so at the output stage we will not be using the resistance at the
output we’ll be using a transformer so this is
VCC 1 and this is your input transformer and first of all we’ll draw the this transformer is connected to the
input that is bass right and this through this resistance I will be
getting the voltage that is plus VCC – right so transformer cos secondary is
connected to the junction of r2 and r1 r3 and r4 rather this is r3 this is our
4 this is RC – this is our e2 will do all the Nama current re1 this is al –
this is r1 right now in this case again we will not be using RC – we will use
the coupling in the form of transformer right similarly we will be getting the
output and the secondary of second stage car transformer right so this is
transformer one right and this is transformer – here what we are dealing
we will get the excellent input on a our input impedance matching cut this part
will be getting excellent impedance matching okay so that is nothing but
your biggest advantage as far as transformer coupling is concerned so we
will say that this is your first stage this is the part which we are dealing
how it is getting connected to the input of second stage okay so this is your
transformer coupling and this is your usual second stage as I have connected
the transformer at the second stage this is your this will be your output that
will be getting and more or less this output also can be connected to the
input of the third stage and so on so here this is the fundamental of your
transformer coupling as well as advantages and disadvantages are
concerned we will just learn few points advantages as I told you excellent impedance input
impedance matching sorry it’s not input impedance excellent impedance matching in matching second is will be getting no
loss of signal in the DC power okay in the terms of DC so signal power which
is nothing but VCC 1 and VCC – that will not get lost so much so no loss of
signal as far as DC power is concerned obviously third very important to assess
customer requirement is concerned will be getting high gain as as compared to
your RC coupling so will be getting high gain now we’ll have to look at the
disadvantages so we’ll learn as whenever you see the transformer whenever you see
the transformer it becomes bulky right so it forms it becomes a bulky in nature secondly costly require more space okay third one is there are high
frequency distortion so which is not at all desirable so we want
the frequency distortion should be very very less right what exactly the
frequency distortion this term we will learn in your power amplifiers that is
chapter number four okay in detail so frequency distortion by the time just
learn in that way we will get this smooth or output for example in your TV
we suppose we are getting all the hands like now the structure is long not clear
in your display of your TV then in previous cases what we used to do we
just change the orientation of the antenna and then suddenly we get the
particular picture so it matches with that particular frequency so if we
change the frequency will not get that that particular output so the frequency
distortion is there in the transformer coupling so we will not usually use the
transformer coupling so these are the advantages these are the disadvantages
so generally we are not using the transformer coupling as far as the
syllabus is concerned we’ll just use the AC coupling either RC coupling or direct
coupling they may ask you the equation about the direct coupling as well there
are few examples dedicated examples which we’ll learn as an RC coupling and
few dedicated examples that we’ll use as an complete direct coupling so we’ll
learn the third part that is third type of coupling that is third is direct
coupling now in this direct coupling it’s it’s
very easy to understand that my first stage does not require any capacitor or
any resistor on any the transformer to connect the output towards the second
stage car input okay so this is directly connected to the input of second stage
it can be your voltage divided by as it can be your self bias it can be a fixed
bias any-any but here generally we used
voltage a otherwise obviously for this ability perspective so here we’ll get
the output and here we’ll get the input if you want the source in input source
resistance then we can connect the source resistance as well this will be
argon will do all nama current so this is our C 1 this is our e 1 this is R 3
this is our 4 this is our C – this is our e 2 so it’s a very very simple
circuit I can say it so now this is nothing but one of these our advantage I
can say it’s a simple circuit so obviously cost effective as well so
let’s learn directly this is nothing but your first stage this is nothing but
your second stage and I can say that this is your direct coupling okay so
let’s learn again the advantages and disadvantages perspective advantages it’s a simple simple circuit second is
also cost effective ok here also we will get good frequency
response and a good impedance matching as well so there are two advantages
simultaneously we’ll be getting good frequency response good frequency response and the fourth
one is good impedance match but as I see advantages are there disadvantages or
limitations has to be there so we will say disadvantages for the direct
coupling disadvantage first is for high frequency I cannot amplify with that
much value as compared to RC and in transformer coupled so at high frequency amplification can’t be achieved okay
efficiency is less what is efficiency whatever we are getting the output right
and what I am giving as input so if we take the ratio of output to input that
is that is nothing but your efficiency an efficiency part in detail we will be
taking in a technical sense in the chapter number 4 that is power amplifier
also so stay tuned for that the efficiency is very very less
and the major reason of this less efficiency is we will be getting the DC
loss because nothing has been connected to the input of first stage and output
of second stage so I can say that current of first stage can get it can
enter into the second stage so I can say the DC power loss is the main reason
main cause for the less efficiency DC power loss okay now the third
disadvantage that will be getting is drift right so drift in the DC amplifier
will laser dip or Q point stability so we will say that for Q point stability
this your Q point stability will need to have not fixed reference point for my
amplification perspective so sometimes you get clipped off output voltage
sometimes you may get the distorted output voltage and that’s how we not use
generally the direct coupling in your circuitry and the practical sense of the
multi stage amplifier but so although these factors will be using this
particular direct coupling in two kinds of transformer that is nothing but
Darlington pair amplifier and your cache mode amplifier okay
so stay tuned for that we will learn more and more EDC to chapter number two
for multi stage amplifier analysis as well as design so learn more and more
EDC tool in this particular videos we have studied RC coupling transformer
coupling and direct coupling so we will stop here in the next videos we will
learn the multi stage amplifier in the design as well as analysis mathematical
perspective so thank you very much for watching this particular video learn
ikura learn cdc2 from ek da videos and be happy thank you so much you

## 11 comments on “Types of Coupling in Multistage Amplifier- Multistage Amplifier – Electronic Devices and Circuits”

1. Khushboo Kumari says:

Nice video thanks sir

2. Ekeeda says:

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3. maneesh gaming says:

Sir hindi m bnao pls

4. Lavkush Lakush says:

Sir hindi m btana plz

5. R DRIFT says:

Tu ads hi hgg le ya video dikha le

6. Jai Garg says:

his hands doesn't match with his face

7. Ankit Raj says:

Bhai thoda short m

8. Rangana Atreya says:

Max of ekeeda video are private why?!

9. Venkateswara Reddy says:

Not informative.. just copying statements from some text book or material… no explanation about advantages and disadvantages

10. Madan Kumar says:

Hlooo sir ,can't u said the working principle and working of the types of all multisatge amplifiers

11. Madan Kumar says:

Hi ,can u plss upload the video of each and every component of the amplifiers in multistage