please help transistor amplifier

michael1978

hi joney, may i ask you something

if we take 10 large then load(50micro)this is all time formula
for i_R2=10*LOAD and I_R1 = 10*Iload + Iload = 11*Iload = 550μA
and
if we take 5 large then load(50micro)this is all time formula
for i_R2=5*LOAD and I_R1 = 5*Iload + Iload = 11*Iload =
is correct?

and can you tell me wich book, do you know some book where i can learn good electronics?
advice
now i am reading electronics principles 7 by malvino

Jony130

Check your algebra skills because your answer is wrong.

B = 5A + A = ??


I don't know any good book. Try buy a book in your native language.

michael1978

is 6 i know now,

but the best books are in engish

michael1978

CAN I KNOW, wich electronic software you use

michael1978

joney my dear, are you here somewhere, i just wana say thank you for help, losing time for me....

Jony130

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.

michael1978

but i dont understand, i have to do experiments, and i dont 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

michael1978

joney is correct this amplifier, he give voltage gain of 44mv not 50mv

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Jony130

I don't know. You need to tell me the bias point collector current and BJT model that you use.

michael1978

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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

Jony130

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:



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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michael1978

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can you explain how you can change the voltage gain by changing Re1
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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 cant 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

yungman

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.

michael1978

thnx for reply, i dont know where to get solution manual by malvino, til now i am to transistor amplifier, but i dont get nothing what joney explain me til now

yungman

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 text book 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.

michael1978

i cant find, but is safe amazone site? can you order it with facture? of only with card

michael1978

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