Please help transistor amplifier

In summary: So, if you choose Ie=1mA, you only have 25Ω to play with, which means you want rl to be very large value, which means you want to use a Darlington transistor.In summary, if you want to design a CE amplifier with a gain of 50, you can use two stages, each with a gain of x10 and x5 respectively. Alternatively, you can use one stage with a gain of 50, but it may be more difficult to design and may not be as reliable. It is important to consider the input and output impedances of the circuit in order to achieve the desired voltage gain.
  • #106
CAN I KNOW, which electronic software you use
 
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  • #107
joney my dear, are you here somewhere, i just wana say thank you for help, losing time for me...
 
  • #108
michael1978 said:
but the best books are in engish
I don't think so.
michael1978 said:
CAN I KNOW, which electronic software you use
I use LTspice, but circuit simulations are not good for beginners.
Circuit simulators are worthless, or worse, if you don't understand your circuit pretty well before you simulate it. Still, it won't hurt you to play with it, so long as you always keep in mind that garbage in = garbage out, or, in the case of simulators, garbage in=sophisticated garbage out.
 
  • #109
Jony130 said:
I don't think so.

I use LTspice, but circuit simulations are not good for beginners.
Circuit simulators are worthless, or worse, if you don't understand your circuit pretty well before you simulate it. Still, it won't hurt you to play with it, so long as you always keep in mind that garbage in = garbage out, or, in the case of simulators, garbage in=sophisticated garbage out.

but i don't understand, i have to do experiments, and i don't have all instruments, in electronics simulator you have all instruments, but me i try examples, but you know better i see you have experience.
thx for answer
 
  • #110
michael1978 said:
thank you very much
joney is correct this amplifier, he give voltage gain of 44mv not 50mv
 

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  • #111
michael1978 said:
joney is correct this amplifier, he give voltage gain of 44mv not 50mv
I don't know. You need to tell me the bias point collector current and BJT model that you use.
 
  • #112
Jony130 said:
I don't know. You need to tell me the bias point collector current and BJT model that you use.


--------
this your example i just simulate (do you see the foto the value) in quote 69

Vb = Ve + Vbe = Ic*(Re1+Re2)+ Vbe = 5mA* (180 + 14) + 0.65V = 1.62V

If we assume Hfe = 150 I (I use transistor 2N3903 I don’t know other there are a lot of types)

Ib = Ic/hfe = 5mA/150 = 34μA

R1 = (Vcc - Vb)/( 11*Ib) = 22KΩ

R2 = Vb/(10*Ib) = 4.7KΩ
Re1 = Rc/Av - re = 1K/50 - 5.2Ω = 20 - 5.2Ω = 14Ω
 
  • #113
But your circuit is different than mine. Also you can read from simulation DC collector current.
And your circuit has a voltage gain equal to:

Av = Vout/Vin = 44.33mV/2mV = 22.165[V/V]

My example look like this:

attachment.php?attachmentid=53268&stc=1&d=1353703873.png


And has a voltage gain Av = 45.8V/V But we can easily change the voltage gain by changing the Re1 resistance.
 

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  • #114
Jony130 said:
But your circuit is different than mine. Also you can read from simulation DC collector current.
And your circuit has a voltage gain equal to:

Av = Vout/Vin = 44.33mV/2mV = 22.165[V/V]

My example look like this:

attachment.php?attachmentid=53268&stc=1&d=1353703873.png


And has a voltage gain Av = 45.8V/V But we can easily change the voltage gain by changing the Re1 resistance.
---------
can you explain how you can change the voltage gain by changing Re1
------------------
Joney do you remember i ask you to make one amplifier with voltage gain of 50, only we Re1 Without Re2,

and you show me this example, look at quote 66, IF YOU HAVE TIME.
Re1 = Rc/Av - re = 1K/50 - 5.2Ω = 20 - 5.2Ω = 14Ω, and i think you did not show me complete example, becuse i am searchin here but i can't find,
do you remember now Re1 = Rc/Av - re = 1K/50 - 5.2Ω = 20 - 5.2Ω = 14Ω
for the rest value i think of maybe i misunderstand , are the same like this circuit the last one... if not ? PLEASE CAN YOU MAKE ONE EXAMPLE ONLY WITH Re1 PLEASE THNX
 
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  • #115
I did not read the whole thread. Remember when I left off, I showed you how to calculate the gain? It's the impedance seen at the collector divided be the impedance seen by the emitter? Adding C2 don't change this, the total emitter resistance is

r'e+ Re1+(Re2//Xc2) where [itex] X_{C2}=\frac 1 {j\omega C}[/itex]

You change the Re2, you change the impedance on the emitter side and change the gain.

You need to get the solution manual of Malvino and work through the problems one by one. I thought I left you in good hands already. There comes a point of time you just work on the problems one by one and struggle through it. You are spending too much time writing posts here instead of working through the problem in the book. These questions are in the book.
 
  • #116
yungman said:
I did not read the whole thread. Remember when I left off, I showed you how to calculate the gain? It's the impedance seen at the collector divided be the impedance seen by the emitter? Adding C2 don't change this, the total emitter resistance is

r'e+ Re1+(Re2//Xc2) where [itex] X_{C2}=\frac 1 {j\omega C}[/itex]

You change the Re2, you change the impedance on the emitter side and change the gain.

You need to get the solution manual of Malvino and work through the problems one by one. I thought I left you in good hands already. There comes a point of time you just work on the problems one by one and struggle through it. You are spending too much time writing posts here instead of working through the problem in the book. These questions are in the book.

thnx for reply, i don't know where to get solution manual by malvino, til now i am to transistor amplifier, but i don't get nothing what joney explain me til now
 
  • #117
michael1978 said:
thnx for reply, i don't know where to get solution manual by malvino, til now i am to transistor amplifier, but i don't get nothing what joney explain me til now

Ha ha! I always gone on the internet and look for free download. You have to do some leg work. I yet to encounter a book that I had not manage to download the instructor or solution manual free yet. This is such a popular book. It is very important to have the solution manual to learn, they show you the steps to get the answer. Now put in your effort and try working out the answer before you peek into the solution manual!

Make sure you get the correct edition, if you manage to download a version you don't have, go on Amazon and find a used textbook of that version. They are very cheap used. I went on Amazon to look for one for you just now and can't find one cheap at the moment. In fact I just ordered a copy of Malvino a few minutes ago just to keep it in my library collection because it's that good. I only paid $US 8.00 including shipping! But you can go on Amazon later and see whether they have a copy cheap.
 
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  • #118
yungman said:
Ha ha! I always gone on the internet and look for free download. You have to do some leg work. I yet to encounter a book that I had not manage to download the instructor or solution manual free yet. This is such a popular book. It is very important to have the solution manual to learn, they show you the steps to get the answer. Now put in your effort and try working out the answer before you peek into the solution manual!

Make sure you get the correct edition, if you manage to download a version you don't have, go on Amazon and find a used textbook of that version. They are very cheap used. I went on Amazon to look for one for you just now and can't find one cheap at the moment. In fact I just ordered a copy of Malvino a few minutes ago just to keep it in my library collection because it's that good. I only paid $US 8.00 including shipping! But you can go on Amazon later and see whether they have a copy cheap.
i can't find, but is safe amazone site? can you order it with facture? of only with card
 
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  • #119
michael1978 said:
---------
can you explain how you can change the voltage gain by changing Re1
------------------
Joney do you remember i ask you to make one amplifier with voltage gain of 50, only we Re1 Without Re2,

and you show me this example, look at quote 66, IF YOU HAVE TIME.
Re1 = Rc/Av - re = 1K/50 - 5.2Ω = 20 - 5.2Ω = 14Ω, and i think you did not show me complete example, becuse i am searchin here but i can't find,
do you remember now Re1 = Rc/Av - re = 1K/50 - 5.2Ω = 20 - 5.2Ω = 14Ω
for the rest value i think of maybe i misunderstand , are the same like this circuit the last one... if not ? PLEASE CAN YOU MAKE ONE EXAMPLE ONLY WITH Re1 PLEASE THNX

hi joney, can you answer me please, because i learn it in serie with Re2, and also in parallel, just with one resistor no i did not learn it, can you take a little time to show me this example, voltage gain 50 with one reistor,like other examples
 
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  • #120
michael1978 said:
i can't find, but is safe amazone site? can you order it with facture? of only with card

I use Amazon ALL the time, The used books are so cheap. I buy so many textbooks, but I never bought them new. When they said the condition is good, it is good. I have two VISA/Mastercard, I use one for everyday, the other JUST for online order like Amazon. So I can track transaction clearly every month. I never have problem.
 
  • #121
yungman said:
I use Amazon ALL the time, The used books are so cheap. I buy so many textbooks, but I never bought them new. When they said the condition is good, it is good. I have two VISA/Mastercard, I use one for everyday, the other JUST for online order like Amazon. So I can track transaction clearly every month. I never have problem.

WHY you can't buy with invoice
 
  • #122
Regarding the circuit. This circuit is a voltage divider bias using R1 and R2 to set up the bias voltage of 10(4.7K/26.7K)=1.76V for Q1 . The emitter of Q1 is about 1.06V. Read this in Malvino. R5 together with R4 is to set up the DC of about 5mA current through Q1 and re' is about 25/5=5ohm. But without C2, gain of the stage is Rc/(Re1+Re2+re')=5. That's very low to be useful.

C2 is to provide a low impedance path to bypass Re2 at higher frequency. With the C2, the gain of the stage is Rc/(re'+Re1+(Re2//Xc)). The impedance of C2 is [itex] X_C=\frac 1 {j2\pi f C}[/itex].

But this is complicated for you. So you can use approximation.

1) At very low frequency, Xc is very high, so you can ignore it. So the gain is Rc/(re'+Re`1+Re2).

2) At frequency where [itex] Re2=\frac 1 {2\pi f C}[/itex], the total resistance of Re2// C2 decrease and the gain of the stage start to rise as show in the graph. It is not important to know the exact frequency as the final gain is usually the important one.

3) As frequency goes higher, Xc is getting lower and lower. Re1<<Re2, you can simplify by ignore Re2. At frequency where [itex] \frac 1 { 2\pi fC}=Re2[/itex], the effect of C2 start to level out. At even higher frequency, C2 can be approximated to be a short circuit( 0 ohm). So at much higher frequency, the gain of the stage is Rc/(re'+Re1) only, as C2 is a short circuit and Re2 is shorted out.

4) the transition frequency where [itex] \frac 1 { 2\pi f C}=R_{e1}[/itex] is usually called [itex]f_c[/itex] where [itex] \frac 1 { 2\pi f_c C}=Re1[/itex] or [itex]f_c=\frac 1 {2 \pi R_{e1} C_2}[/itex]. You can see the point of fc where the graph of the gain start bending horizontal to level out.

Hope this help. This is an approximation. For more accurate calculation, you really have to use complex number, but believe me, it's good enough. I use this all these years for my own design at work.
 
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  • #123
michael1978 said:
WHY you can't buy with invoice

I never try that and sounds more complicate. You enter the credit card info the first time to set up the account, after that, you just login and it will do it for you. You never have to enter the credit card info again.
 
  • #124
yungman said:
Regarding the circuit. This circuit is a voltage divider bias using R1 and R2 to set up the bias voltage of 10(4.7K/26.7K)=1.76V for Q1 . The emitter of Q1 is about 1.06V. Read this in Malvino. R5 together with R4 is to set up the DC of about 5mA current through Q1 and re' is about 25/5=5ohm. But without C2, gain of the stage is Rc/(Re1+Re2+re')=5. That's very low to be useful.

C2 is to provide a low impedance path to bypass Re2 at higher frequency. With the C2, the gain of the stage is Rc/(re'+Re1+(Re2//Xc)). The impedance of C2 is [itex] X_C=\frac 1 {j2\pi f C}[/itex].

But this is complicated for you. So you can use approximation.

1) At very low frequency, Xc is very high, so you can ignore it. So the gain is Rc/(re'+Re`1+Re2).

2) At frequency where [itex] Re2=\frac 1 {2\pi f C}[/itex], the total resistance of Re2// C2 decrease and the gain of the stage start to rise as show in the graph. It is not important to know the exact frequency as the final gain is usually the important one.

3) As frequency goes higher, Xc is getting lower and lower. Re1<<Re2, you can simplify by ignore Re2. At frequency where [itex] \frac 1 { 2\pi fC}=Re2[/itex], the effect of C2 start to level out. At even higher frequency, C2 can be approximated to be a short circuit( 0 ohm). So at much higher frequency, the gain of the stage is Rc/(re'+Re1) only, as C2 is a short circuit and Re2 is shorted out.

4) the transition frequency where [itex] \frac 1 { 2\pi f C}=R_{e2}[/itex] is usually called [itex]f_c[/itex] where [itex] \frac 1 { 2\pi f_c C}=Re2[/itex] or [itex]f_c=\frac 1 {2 \pi R_{e1} C_2}[/itex]. You can see the point of fc where the graph of the gain start bending horizontal to level out.

Hope this help. This is an approximation. For more accurate calculation, you really have to use complex number, but believe me, it's good enough. I use this all these years for my own design at work.

thank for time, but i want just with r'e and re1 without re2 the voltage gain about 50mv, the procedure which show me joney,
 
  • #125
yungman said:
I never try that and sounds more complicate. You enter the credit card info the first time to set up the account, after that, you just login and it will do it for you. You never have to enter the credit card info again.

yes but maybe in once some hacker can take your credit, but do you know which card can accept amazone?
 
  • #126
michael1978 said:
thank for time, but i want just with r'e and re1 without re2 the voltage gain about 50mv, the procedure which show me joney,

As I explained, at frequency above fc, the reactance of C1 is very low and you can just calculate using r'e and Re1.

For example, if C1 is 100uF, at 1KHz, Xc=1/(2\pi f C)=1.59ohm. 1.59 ohm is so much lower than 180 of Re2. When parallel with Re2, Re2 disappeared. So you only have Re1 and r'e left.
 
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  • #127
michael1978 said:
yes but maybe in once some hacker can take your credit, but do you know which card can accept amazone?

Well, you always are taking a chance. But if you have a good password, that would protect you. Email to Amazon and ask them. Now a days, if you don't use online, you are missing the world.
 
  • #128
yungman you made a small mistake. I suspect a typo error.
If we assume that C1 and C3 >> C2 and Re1 << Re2
So now we can find corner frequency as:

[itex]\Large Fc\approx \frac{0.16}{(re+Re1)*C2}[/itex]
 

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  • #129
Yes, in 4), it should by Re1. I change the 2 to 1 already.
 
  • #130
yungman said:
As I explained, at frequency above fc, the reactance of C1 is very low and you can just calculate using r'e and Re1.

For example, if C1 is 100uF, at 1KHz, Xc=1/(2\pi f C)=1.59ohm. 1.59 ohm is so much lower than 180 of Re2. When parallel with Re2, Re2 disappeared. So you only have Re1 and r'e left.

YOUNGMAN, i learn from joney step by step procedure, its is difficult to understand yours because joney he make in very similary way, biasing gain , step by step, do you see his examples, but he don't answer me anymore i don't know why
do you know to build one amplifier like joney step by step without re2
 
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  • #131
Jony130 said:
yungman you made a small mistake. I suspect a typo error.
If we assume that C1 and C3 >> C2 and Re1 << Re2
So now we can find corner frequency as:

[itex]\Large Fc\approx \frac{0.16}{(re+Re1)*C2}[/itex]

yes he make mistake you see he teach me bad hahaha i am just joking, joney why you don't answer me? WHATS WRONG?,
 
  • #132
michael1978 said:
joney why you don't answer me? WHATS WRONG?,
Because I and yungman gave you all information you need to know to design simple BJT amplifier with or without Re2 resistor.
 
  • #133
Jony130 said:
Because I and yungman gave you all information you need to know to design simple BJT amplifier with or without Re2 resistor.

no joney rely, i understand all, with re re1 re2 in serie, and also in parallel re1 and re2, but this only with re1 without Re2 , i rely don't understand, you show every example step by step, but with re1 i can't find it, i am searching in quote from the beginin but i can find, RELY otherwise i with not ask you , i ask you in qoute 5, to make one example but you did not complete of me i don't understand, rely i with not ask you anymore if i know it, because you show me complete procedure of amplifier with re1 re2 in parallel and in serie and i understand, only this one no, only with re1, for that i am asking so long and i am whaiting answer from you, like i see you make it very quickly, just one more without re2
AND IS DIFFICULT TO UNDERSTAND SOMEBODY ELSE WITH A LOT OF EQUATION, please can you make one more thnx for reply
 
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  • #134
But why you don't want to try and use this information we have give you and start design amplifier without Re2 resistor. Once at least TRY to answer your own question and show SOME work, instead of expecting people here to be your no-effort-required-on-your-part answering service
 
  • #135
Jony130 said:
But why you don't want to try and use this information we have give you and start design amplifier without Re2 resistor. Once at least TRY to answer your own question and show SOME work, instead of expecting people here to be your no-effort-required-on-your-part answering service

that is right Joney but like i ask all time for example voltage gain of 50, is just to know steps how to make an amplifier and to do experiments in simulation, with other value, for example gain of 20 of 10, of other value of biasing etc, but i see the best was first to learn only with one resistor with re1, and after in serie and in parallel, for that i ask you, because this what you show me til now, i don't have in my book electronics principle 7 by malvino, and i read also some other book about microelectronics, there don't exist your example, i search it a lot in internet but pblackblack nothing i find, is possible for you just one more and after i with start experiments PLEASE
 
  • #136
yungman said:
I never try that and sounds more complicate. You enter the credit card info the first time to set up the account, after that, you just login and it will do it for you. You never have to enter the credit card info again.

but is that possible of not
 
  • #137
michael1978 said:
no joney rely, i understand all, with re re1 re2 in serie, and also in parallel re1 and re2, but this only with re1 without Re2 , i rely don't understand, you show every example step by step, but with re1 i can't find it, i am searching in quote from the beginin but i can find, RELY otherwise i with not ask you , i ask you in qoute 5, to make one example but you did not complete of me i don't understand, rely i with not ask you anymore if i know it, because you show me complete procedure of amplifier with re1 re2 in parallel and in serie and i understand, only this one no, only with re1, for that i am asking so long and i am whaiting answer from you, like i see you make it very quickly, just one more without re2
AND IS DIFFICULT TO UNDERSTAND SOMEBODY ELSE WITH A LOT OF EQUATION, please can you make one more thnx for reply

Read my post #122, I explained step by step why at high frequency, Re2 disappeared. The explanation is adding on top of what Jony130's diagram and all. You really need to stop and work it out step by step, put in some numbers and work it out.

BTW I still miss one on 3). Re2 should be Re1.

You need to show some effort, use the number Jony130 gave in the diagram and show us your calculation. Whether it is correct or not, show you try to solve the problem. I help you at the beginning, together with Malvino, you should be able to get started. But after 9 pages of question and answer, you are still pretty much on the same circuit with the addition of C2 and Re2!

Work out some numbers and people are more than happy to help.
 
  • #138
michael1978 said:
but is that possible of not

I don't know what else to say, you need resources, but you don't want to take any chances. I don't think you can just walk into a book store and find what you want and pay cash! At some point, you are going to have to trust something.

If you are worry, do what I am doing, get a credit card with low limits, use that only for online order. So if you get scam, you know right away and it will be minimal loss.

Did you try looking online for free download?
 
  • #139
yungman said:
I don't know what else to say, you need resources, but you don't want to take any chances. I don't think you can just walk into a book store and find what you want and pay cash! At some point, you are going to have to trust something.

If you are worry, do what I am doing, get a credit card with low limits, use that only for online order. So if you get scam, you know right away and it will be minimal loss.

Did you try looking online for free download?

yes i try to download online, via google
 
  • #140
michael1978 said:
that is right Joney but like i ask all time for example voltage gain of 50, is just to know steps how to make an amplifier and to do experiments in simulation, with other value, for example gain of 20 of 10, of other value of biasing etc, but i see the best was first to learn only with one resistor with re1, and after in serie and in parallel, for that i ask you, because this what you show me til now, i don't have in my book electronics principle 7 by malvino, and i read also some other book about microelectronics, there don't exist your example, i search it a lot in internet but pblackblack nothing i find, is possible for you just one more and after i with start experiments PLEASE

ok JONEY SORRY, i read in post 77, i read and i read and you show me example good, but i don't understand why you add re2, and you don't have to calculate in gain? i will try to make one example
 
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<h2>1. What is a transistor amplifier?</h2><p>A transistor amplifier is an electronic device that uses transistors to amplify an electrical signal. It is commonly used in electronic circuits to increase the strength of a weak signal.</p><h2>2. How does a transistor amplifier work?</h2><p>A transistor amplifier works by using a small current to control a larger current. This is achieved by applying a small input voltage to the base of the transistor, which then allows a larger current to flow from the collector to the emitter. This amplifies the signal.</p><h2>3. What are the benefits of using a transistor amplifier?</h2><p>Transistor amplifiers offer several benefits, including high gain, low distortion, and high input impedance. They are also small in size and require low power, making them ideal for use in portable electronic devices.</p><h2>4. What are the different types of transistor amplifiers?</h2><p>There are three main types of transistor amplifiers: common emitter, common base, and common collector. Each type has its own unique characteristics and is used for different applications.</p><h2>5. How do I choose the right transistor amplifier for my project?</h2><p>When choosing a transistor amplifier, it is important to consider factors such as the desired gain, frequency range, and input and output impedance. It is also important to select a transistor with a suitable power rating for your project.</p>

1. What is a transistor amplifier?

A transistor amplifier is an electronic device that uses transistors to amplify an electrical signal. It is commonly used in electronic circuits to increase the strength of a weak signal.

2. How does a transistor amplifier work?

A transistor amplifier works by using a small current to control a larger current. This is achieved by applying a small input voltage to the base of the transistor, which then allows a larger current to flow from the collector to the emitter. This amplifies the signal.

3. What are the benefits of using a transistor amplifier?

Transistor amplifiers offer several benefits, including high gain, low distortion, and high input impedance. They are also small in size and require low power, making them ideal for use in portable electronic devices.

4. What are the different types of transistor amplifiers?

There are three main types of transistor amplifiers: common emitter, common base, and common collector. Each type has its own unique characteristics and is used for different applications.

5. How do I choose the right transistor amplifier for my project?

When choosing a transistor amplifier, it is important to consider factors such as the desired gain, frequency range, and input and output impedance. It is also important to select a transistor with a suitable power rating for your project.

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