Electronics Questions

[Keshooo]

الموضوع ده للأسئله

:)

[Keshooo]

سؤال بسيط بس انا ناسي

هوا ليه ال freq resp عند Wc بيساوي -ve 3 db

ليه negative

[No Name]

at Wc -> Gain=1/root(2) of midband gain
20log (1/root 2)=-3

[yousef]

since at Wc the gain drops to half of it is original value
and when you transfer half to dB you get -3dB
it is -3dB from the original dB of the gain
and negative because it is in the denominator i.e(<1).

[Keshooo]

at Wc -> Gain=1/root(2) of midband gain
20log (1/root 2)=-3

ah tamam eftakart

thanks
:)

[Keshooo]

دلوقتي هوا ال pole بيزود ال slope ولا يقلله

يعني ال pole يخلي ال slope .. negative walla positive

علشان انا كاتب في السكشن حاجه و السكشن اللي نازل هنا عكسي ؟؟؟؟ :S

[planète bleue]

أنا كنت لسة يا بشمهندس هنزل Note للغلطة دي في السيكشن :)

هي فعلا مكتوبة غلط في السيكشن ..

the pole makes the slope to decrease and the zero makes the slope to increase

سيتم تثبيت الموضوع :)

thanks keshooo ;)

[No Name]

negative

[planète bleue]

هو لما يزيد ب 20 dB من الزيرو هيكون +ve ولما يقل ب 20 dB من الزيرو يبقة -ve ..

يعني اللي أقصده الناس متاخدهاش أنه هيكون -ve أو +ve ... بس تمشوا مع ال poles and zeros وتاخدو في اعتباركوا ال 20dB ..

يعني مثلا لو جالي زيرو زودلي ال slope ب 20 dB وبعدها جالي pole نقصهولي 20 dB يبقة ال slope هايرجع زيرو تاني .. أكيد يعني :D

بالنسبة لموضوع ال -ve و ال +ve :

لما يجيلي زيرو الخط هايطلع لفوق يعني ال slope هيكون موجب .. ولما يجيلي pole الخط هاينزل لتحت يعني ال slope هيكون بالسالب ..

بس كدة ..

[Mahmoud Amr]

انا متأسف يا جماعة على الخطأ اللى موجود فى السكشن
ان شاء الله بكرة هتنزل ملزمة فيها تصحيح الكلام دة و شوية ملاحظات تانية

[Keshooo]

أنا كنت لسة يا بشمهندس هنزل Note للغلطة دي في السيكشن :)

هي فعلا مكتوبة غلط في السيكشن ..

the pole makes the slope to decrease and the zero makes the slope to increase

سيتم تثبيت الموضوع :)

thanks keshooo ;)

well ,

welcome
and thanks for help

:)

[Keshooo]

why

Vce=Vceq - Vpsinwt

why
-Vp

??

[planète bleue]

i think because current direction is in opposite direction with the voltage ...

[Keshooo]

هوا يعني ايه
@ Vcc/2 MAX symmetrical swing

????????????????????

thanks in advance :)

[planète bleue]

هو الكلام ده في محاضراتي :D ؟

احم .. هو أنا الحقيقة معرفش يعني ايه الجملة ذات نفسها .. بس اللي أعرفه أن عند Vcc/2 بيكون عندي best performance ...

[elec-tric]

. maximum symmetrical swing occurs only when Vce=Vcc/2
so when you put an input signal, Vce can change from zero to Vcc which is the maximum symmetrical
swing
bas keda :D

[egyeng]

Is there any difference between the small signal( Normal Amplifier) voltage gain and the large signal(Power Amplifier) voltage gain and the way they're to be calculated ?
As i know for the normal CE Amplifier the gain Av = -Beta(Rout)/Rin
Is this expression valid for both signals ( small and large ) When we are calculating the voltage gain (Av) ? :) i hope to get an Answer
Thank u in Advance :)

[amr.attaby]

the gain Av = -Beta(Rout)/Rin


this is valid only when transistor is in active region, just make sure b4 using it.

If you understand this well, then please answer your question.

Regards,

Amr Attaby

[sweetangel]

In sheet 3 problem (6) no (b) I cant understand how the feedback is done here? Thank u in advance Eng/Amr

[beauty]

in sheet(3 problem 2

letter(d)
adding Rs in parallel with Is.how 'll it affect the Ro ?
thanks)

[egyeng]

Thank you Eng/Attaby my problem is resolved i was Confused with something else

[AhmedElSayed]

Tab a question in class-B PA:

What happens when Vin exceeds Vcc+0.3 for example ??

Vo = Vin-VBE = Vcc-0.2 (assuming VBE = 0.5) then Qn would go into saturation and VCE|sat =0.2

I can see that if Vin exceeds this value, then either Vo would increase and thus VCE|sat would decrease below 0.2 (how?)
or Vo would not change, and VBE would be greater than 0.7( how?)


I want to know what will happen exactly to Vo and to Qn, would it burn due to this conflict ?

Thanks in advance

[amr.attaby]

why

Vce=Vceq - Vpsinwt

why
-Vp

??

It is better to use Vce = Vc - Ve = Vcc - Vout = Vcc - Vp*sin(wt)

Regards,

[amr.attaby]

. maximum symmetrical swing occurs only when Vce=Vcc/2
so when you put an input signal, Vce can change from zero to Vcc which is the maximum symmetrical
swing
bas keda :D

correct

[amr.attaby]

Tab a question in class-B PA:

What happens when Vin exceeds Vcc+0.3 for example ??

Vo = Vin-VBE = Vcc-0.2 (assuming VBE = 0.5) then Qn would go into saturation and VCE|sat =0.2

I can see that if Vin exceeds this value, then either Vo would increase and thus VCE|sat would decrease below 0.2 (how?)
or Vo would not change, and VBE would be greater than 0.7( how?)


I want to know what will happen exactly to Vo and to Qn, would it burn due to this conflict ?

Thanks in advance

Practical case: -

Any node in the circuit can't be increase on Vcc even the input becuase it must be coming from another circuit with V< Vcc
Exception: 1- If we have a coil
2- If we have two +ve supplies at the circuit Vcc1 and Vcc2

for your 2nd Qn:
the transistor will keep in saturation

[amr.attaby]

In sheet 3 problem (6) no (b) I cant understand how the feedback is done here? Thank u in advance Eng/Amr

Look at the circuit without M2...

It is normal Common Source Amplifier.

beta-network = M2

Sampling = Voltage Sampling cuz M2 gate is connected to Vout.

Mixing: current cuz M2 source current is mixed to Iin

beta = Iout/Vin = gm2

Ribeta = ro for M2

Robeta = inf "gate resistance"

[amr.attaby]

in sheet(3 problem 2

letter(d)
adding Rs in parallel with Is.how 'll it affect the Ro ?
thanks)

u mean sheet 4,

adding Rs will affect A-circuit gain

Rof = Ro / (1+beta*A)

since A will change --> Rof will change

[amr.attaby]

please don't ask i a separate topic again

for moderators: pls. mix this topic with the pinned Qn topic

[AhmedElSayed]

Practical case: -

for your 2nd Qn:
the transistor will keep in saturation

so Vbe will exceed 0.7 in that case ?? how could this happen ??

[zeeco]

when can we use pi model & T model of BJT small signal models & where ??

[planète bleue]

in sheet 4 no.2

letter d

what is the effect of Rs when it's in parallel with the current source?

[beauty]

upppp
u mean sheet 4,

adding Rs will affect A-circuit gain

Rof = Ro / (1+beta*A)

since A will change --> Rof will change

[Kamal]

أنا مش فاهم بس يا بشمهندس الجزئية اللي عملناه في اخر سكشنين في PA

في الجزئية اللي بيقولي فيها لو شيلت Vcc- إيه اللي هيحصل في max swing وبقية السؤال

دلوقتي ليه عملنا التوصيلة بالطريقة ديه ... يعني ليه وصلنا بطارية قيمتها بالتحديد Vcc/2 فيo/p ... وفي مسألة 2 ... ليه حطيت في دايرة اللي من غير coil المقاومة ب
RL*2

وقيمة ال SWING هتبقي كام

من الآخر عشان أريح حضرتك ... لو حضرتك تحليلنا الجزئية ديه في اخر مسالة 2 و اخر مسالة 6 بالتفصيل (مع ذكر أسباب التغييرات ديه وازاي عملناها )عشان مش واضحة بالنسبالي من السكشن بشكل كبير ... لأنها كانت في آخر السكشن وما فصلناش فيها كتير

[amr.attaby]

when can we use pi model & T model of BJT small signal models & where ??

normally, both should be OK in any case ...
but in CE & CC case --> pi-model is easier
while in CB case --> T-Model is easier

---


أنا مش فاهم بس يا بشمهندس الجزئية اللي عملناه في اخر سكشنين في PA

في الجزئية اللي بيقولي فيها لو شيلت Vcc- إيه اللي هيحصل في max swing وبقية السؤال

دلوقتي ليه عملنا التوصيلة بالطريقة ديه ... يعني ليه وصلنا بطارية قيمتها بالتحديد Vcc/2 فيo/p ... وفي مسألة 2 ... ليه حطيت في دايرة اللي من غير coil المقاومة ب
RL*2

وقيمة ال SWING هتبقي كام

من الآخر عشان أريح حضرتك ... لو حضرتك تحليلنا الجزئية ديه في اخر مسالة 2 و اخر مسالة 6 بالتفصيل (مع ذكر أسباب التغييرات ديه وازاي عملناها )عشان مش واضحة بالنسبالي من السكشن بشكل كبير ... لأنها كانت في آخر السكشن وما فصلناش فيها كتير

I think you will get a detailed answer when sheet 2 solution released. just wait cuz there are a lot of cts need to be drawn to answer this Qn. and I wrote these details to the students that will release the sheet answer.

Regards,

[zeeco]

شكرا يا باشمهندس جزاك الله خيرا

[a7med.elhaddad]

in sheet 4
problem 1
Eng Amr you calculated the open loop gain A=1970.8 how comes ?as I tried to calculate it again it was 1294.1
Thanks in advance.
:^^:

[Mahmoud Amr]

me too
i calculated it again and A = 1293.65

[amr.attaby]

in sheet 4
problem 1
Eng Amr you calculated the open loop gain A=1970.8 how comes ?as I tried to calculate it again it was 1294.1
Thanks in advance.
:^^:

We calculated it together in the section... The calculations were done by some of you :D ... of course we may made a calculation mistake in the section especially if many of u got the same answer.

[tornado]

I wanted to know when will the solutions of the sheets become available??
Thanks

[Mahmoud ABD el LATIF]

a question

in SEDRA problems Chapter 8 problem 8.1

given A=100
Af=10

A is educed by 20 %

calculate dAf/Af

i said that Af= A/(1+B.A) and get that 1+B.A= 10
then B is calculated
dAf/Af = dA/A / (1+B.A) so dAf/Af f= 2 % and Sedra m3amalsh kda :sad:

is the concept here is to use A afterreduction in the law ?? like solution in SEDRA

[Keshooo]

ro=VA/Ic

aih el VA
??

we in T Model :

1/gm
=re

aih re
??


thanks in advance
:)

[mmtaa_1989]

لية مفيش dc power فى class B وليةvp max=vcc ؟؟؟
thx plz any one answer me

[Mahmoud ABD el LATIF]

ro=VA/Ic

aih el VA
??

we in T Model :

1/gm
=re

aih re
??


thanks in advance
:)


VA

early voltage


التاني بقا جرب تبص في المحاضرة كدا يمكن تلقاها

[amr.attaby]

a question

in SEDRA problems Chapter 8 problem 8.1

given A=100
Af=10

A is educed by 20 %

calculate dAf/Af

i said that Af= A/(1+B.A) and get that 1+B.A= 10
then B is calculated
dAf/Af = dA/A / (1+B.A) so dAf/Af f= 2 % and Sedra m3amalsh kda :sad:

is the concept here is to use A afterreduction in the law ?? like solution in SEDRA
could u tell me what Sedra did?

However,

If I'm going to solve this problem, I won't use the rule u used because this rule came from diffrentiation with required small change to be accurate, but the change here is 20% which is not small.

I'll solve by the more direct and easier method as following:

10 = 100/(1+100B) --> B=0.09
after gain reduction: A2 = A * (1-20%) = 80
thus, Af2 = 80/(1+0.09*80) = 9.756
delta Af = 0.244
delta Af / Af = 2.44%

notice the error btn the two answers.

this way is more accurate.

regards,

[amr.attaby]

ro=VA/Ic

we in T Model :

1/gm
=re

aih re
??
:)

resistance from emmitter to base

[amr.attaby]

لية مفيش dc power فى class B وليةvp max=vcc ؟؟؟
thx plz any one answer me


1- because the transistor Q-point is adjusted at zero current.

2- because the maximum output voltage can't exceed Vcc, other wise we will have supply clipping.

[Mahmoud ABD el LATIF]

could u tell me what Sedra did?

However,

If I'm going to solve this problem, I won't use the rule u used because this rule came from diffrentiation with required small change to be accurate, but the change here is 20% which is not small.

I'll solve by the more direct and easier method as following:

10 = 100/(1+100B) --> B=0.09
after gain reduction: A2 = A * (1-20%) = 80
thus, Af2 = 80/(1+0.09*80) = 9.756
delta Af = 0.244
delta Af / Af = 2.44%

notice the error btn the two answers.

this way is more accurate.

regards,


thanks and i found it in section but i forgot




question in lectures
lecture 5 i found an example in AB class

2- IQ ???

i didnt understand the soln


thanks mo2adaman (in advance)

[aalsons]

In feedback pbs when we calculate A from AC model we always divide the o/p by the i/p. Isn't this the closed loop gain Af ??
I think we must divide the o/p by the i/p of the basic amplifier not the external i/p signal

[ahmad12]

in solved example 8.2 in sedra i dont know how he got Ro
i think it should be Ro=Req parallel (r(pi)+Rc)/beta+1
but in the book he is adding them not making them parallel
shouldnt i when i transfer a resistance from base to emitter i divide by beta+1 then make it parallel with the resistance existing in the emitter ??

[amr.attaby]

In feedback pbs when we calculate A from AC model we always divide the o/p by the i/p. Isn't this the closed loop gain Af ??


no it is the openloop gain because the FB n/w is removed --> i.e loop is open

[amr.attaby]

for ahmad12 pls, bring the example u r talking about

[Keshooo]

هو el-practical wel-ideal بتاع el-circuits
الاثبات بتاعهم يعني ممكن يجي

ولا اللي هيجي كله مسائل ؟؟؟؟؟

يعني ممكن ييجي يقولي اثبت el-Ri و Ro في الفدباك و كده ؟؟؟؟

thanks in advance
:)

[Keshooo]

في example 2 في sheet 4

why in sampling when we put Vo=0 , If = 0

ليه يعني ؟؟؟؟؟؟؟؟؟؟؟؟؟؟؟

[Keshooo]

ليه رسمة el-Vce مختلفة في
direct couple
عن inductor coupled

???????????????

[nourihan]

sheet 4 7 b) how did i transfer from the previous eq. in the o/p loop to reach this
il*(1+gm(Rl+Rm)))=gm vx

[Islam Elshahat]

هو el-practical wel-ideal بتاع el-circuits
الاثبات بتاعهم يعني ممكن يجي

ولا اللي هيجي كله مسائل ؟؟؟؟؟

يعني ممكن ييجي يقولي اثبت el-Ri و Ro في الفدباك و كده ؟؟؟؟

thanks in advance
:)

هو الدكتور قال في المحاضرة أنه ممكن يجيب مسألة على الكلام general اللي في الأول وقال أنه ممكن يطلب أنك تثبت العلاقات قبل ما تستخدمها في المسألة بس تثبتها على بلوكات زي المحاضرة مش على الدايرة بتاعة المسألة

[planète bleue]

طب ايه لزمة الشيتات بقة :s

[amr.attaby]

ASA,

I didn't found a time to check the rest of your questions yesterday before the exam. So forgive me for that. and thanks Islam for your attitude to help in answering the question.

Regards,

[tamara]

ممكن يا بشمهندس عمرو عتابى حضرتك تعمل التكاملات بتاعت الpl,pdc,pin لكل الPA's او لبعضهم عشان معظم التكاملات بتطلع معايا غلط......والدكتور ممكن يجيب الاثباتات فى الامتحان.......شكرا

[planète bleue]

in lec.6 page 4

equation 4

مرضيتش تطلع معايا لما عملتها بالتكامل !

فيه حد طلعت معاه ؟؟

[planète bleue]

اه صحيح أنا طلعت معايا بنص القيمة بتاعة eq.4

[yousef]

simply by substituting ic with Ip*Cos(Wt) and then note it is from zero to phi not pi
and from the triangular identity Cos^2(Wt) = 0.5(1-2Cos(2Wt))you can integrate

You can use the method that eng amr attaby used see sec 7

the Id which is the DC component will be eliminated since the integration on cos from -phi to phi which is sin(phi)-sin(-phi) =zero

[beauty]

ASA,
cld anyone tell me plz to which page shld we study in the compansation part & in chapter 13 in da refrence?
thx alot

[planète bleue]

simply by substituting ic with Ip*Cos(Wt) and then note it is from zero to phi not pi
and from the triangular identity Cos^2(Wt) = 0.5(1-2Cos(2Wt))you can integrate

You can use the method that eng amr attaby used see sec 7

the Id which is the DC component will be eliminated since the integration on cos from -phi to phi which is sin(phi)-sin(-phi) =zero

مش معمولة على فكرة في السيكشن !

طيب ازاي التكامل من 0 ل pi ! في أول سطر من الصفحة التالتة في sec.7

[Mahmoud ABD el LATIF]

a question plz

in sedra soln

problem 8.42

gm = 2 ID / Von
!!???


http://www.h3sonline.com/forums/attachment.php?attachmentid=3682&stc=1&d=1274467336


-------------------------------------------------------------------------
onther problem

how to know the topology :sad:

http://www.h3sonline.com/forums/attachment.php?attachmentid=3683&stc=1&d=1274467342

[planète bleue]

how to know the topology, see the couple of papers before Question.6 solution in sheet3 solution

[Mahmoud ABD el LATIF]

طيب على هذا الاساس طلعت المسالة التانية ال
B---> mho

ازاي احدد قيمتها بقا عشان مش عارف ؟!! و فكرت كتير و م عرفتش

[reham]

MMKN LW 7D FAHM EL COMPENSATION Y2OLHALY
Y3NE EL AWL BNZL MN ENHY NO2TA WLA BTL23 MNEN EH 7'TAWTHA BLZABT ???

[فهد]

سؤال غريب
بس انا حاسس انى تايه فى جزء دكتور اسماعيل
ممكن حد يقول ايه بالظبط اللى احنا خدناه فى المحاضره والسكاشن من بعد الميد تيرم

يا ريت فعلا حل يرد
وميقلش دور انت :lol:

[فهد]

ممكن حد يقول ايه اللى علينا فى الـــ Slides بتاعت الــ Noise لانها كبيره اوى 44 صفحه
وكمان فى Slides تانيه اسمها Class D كبيره اوى برضه ( ديه علينا ولا ايه ) ؟

[planète bleue]

follow the lectures and sections plz

[فهد]

طيب
والله انا عارف
طيب
بالنسبه للطلب التانى بتاع الـــ Slides
ممكن حد يقول ؟

[reham]

هو محدش رد على سوالى لية؟؟؟؟؟؟؟

[planète bleue]

والله أنا لسة مبدأتش مذاكرة الجزء ده أصلا يا بشمهندسة :sad:

[reham]

والله أنا لسة مبدأتش مذاكرة الجزء ده أصلا يا بشمهندسة :sad:
ولا يهمك يا توتو المهم انك رديتى

[reham]

طيب يا جماعه اللى زاكر الجزء ده وعرف سوالى اللى فات يرد ويجاوبنى على السوال ده كمان ربنا يخليكوا للمنتدى بقا
السوال التانى
delw2ty asln kl pole bt3ml decrease ll phase (pi/2) ok de mtf2en 3aliha delw2ty b2a fe el sec el m7lol fe pb 3 sheet 6 fe 2 poles el pole el tania el phase 3ndha m3mol -180 ezay ????? 7d fhm el so2al??

[planète bleue]

ولا يهمك يا توتو المهم انك رديتى

لو كنت أعرف إنك بتحبي ردودي كنت رديت من زمان :D

[Λ7MD]

هو الدكتور إسماعيل شرح في الـ slides لغاية slide رقم 26 ؟

و الباقي؟

[beauty]

ASA,
in case of current sampling(o/p series) where shld i take the output resistance?
if anyone solved no 4 in sheet FB 'll really help if he(she) gave me the final answer.
thx alot

[amr.attaby]

ASA,
in case of current sampling(o/p series) where shld i take the output resistance?
if anyone solved no 4 in sheet FB 'll really help if he(she) gave me the final answer.
thx alot

o/p resistance that o/p current can see

[amr.attaby]

a question plz

in sedra soln

problem 8.42

gm = 2 ID / Von
!!???









could you please calculate gm for MOSFET ?

I = 0.5*mu_n*C_ox*W/L* (Vgs-Vth)^2

gm = dI/dVgs

bring a paper and pen to make the differentiation

now remove (Vgs - Vth) in terms of current I

you will get

gm = 2*I/(Vgs-Vth)

Some references like Sedra like to name Von=Vgs - Vth

please If you understand the answer upload the derivation you made so that you can help your friends

by the way, this rule is the general rule for MOSFET gm







onther problem

how to know the topology :sad:

http://www.h3sonline.com/forums/attachment.php?attachmentid=3683&stc=1&d=1274467342

Voltage Sampling - Current Mixing

beta network : 100k & 1k & 1k between Vo, Vn

beta = I_out / Vin

I_out = Vin/(100k+1k//1k)*(1k/(1k+1k)) current divider law

so beta = 1/(0.5*100.5k) ~20uS

got it?

[amr.attaby]

ممكن يا بشمهندس عمرو عتابى حضرتك تعمل التكاملات بتاعت الpl,pdc,pin لكل الPA's او لبعضهم عشان معظم التكاملات بتطلع معايا غلط......والدكتور ممكن يجيب الاثباتات فى الامتحان.......شكرا


sorry,

but you are a student in 3rd year Communications and should be able to make the integration correctly !!

We just make integration for either "sin" or "sin^2" or "sinx*siny", You should be able to do them and harder when you were in preparatory year !!

If you couldn't make them alone, then It is really a series problem. and I advice to pay some time to make them, they are not hard on your level.

I hope you tell me that you made them alone and they were easy... :)

waiting for your reply ... :)

[tamara]

ouch.................thanks

[khalil]

if anyone solved the questions of sedra in the parts of stability and feedback i want to know what is the most important problems

cause i have no time and it is a donkey work to start solving all of them now
:D:D
Regards

[planète bleue]

not meeeeeeee :petlya35ch: