please help me with transistor amplifier

[michael 1978]

why when i make simulation file in multisim i get other rezultat of voltage gain

what i have to do in multisim to get the same resultat thnx

 

[goldsmith]

Dear michael
Hi
Do you expect that the gain for both circuits be the same ? is that your design ? or a homework ? if it is your design , can you show me the design , steps , thus i can find the error .
Best Wishes
Goldsmith

 

[michael 1978]

hey goldsmith thnx for replying

no, i am trying to learn tranisitor amplifier

i am reading one book

and i have a multsim, i try the first example with the input signal of 2mv
and i dont get the voltage gain of 117 total 234 mv
but i get voltage gain in multisim 22.423 mv, the 3 capacitors are the size of 1uF

what to do, can you please help me, wich steps to follow to make an amplifier PLEASE THANK YOU

 

[LvW]

Hi Michael,

at first, do not expect to get exactly the same result as calculated, because it depends on the transistor type. Not all transistors are identical.
If both results (simulation vs. calculation) are equal within +-(10...30)% it is OK.
Secondly, dont forget the frequency! Because of the capacitor across the emitter resistor you have negative feedback for the low-frequency region.
I assume you have tested for very low frequencies.
Try an ac analysis (gain vs. frequency) and you will see the frequency dependence of the gain.
Good luck
LvW

 

[michael 1978]

hi lvw
i take that example from book
so i put the value of capacitors self

because he did not put the value of capacitors in circuit, maybe i make mistake in value of capacitors
thnx for reply

- - - Updated - - -

hi lvw
i take that example from book
so i put the value of capacitors self

because he did not put the value of capacitors in circuit, maybe i make mistake in value of capacitors
thnx for reply

 

[goldsmith]

Hi michael
I suppose that your amplifiers have been designed for audio range , so i think if you use 1000 uf capacitors the result will be better . test it and show us the result .
As "LvW" said , the frequency is important it should be short circuit instead of your BW ( estimated ! )
Best Wishes
Goldsmith