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Old 20th February 2007, 03:23 PM   #1
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Default problem with preamplifier simulation

Hi to everybody!

I'm trying to simulate this preamplifier (it's a project that i posted some time ago on this forum) but from the AC-sweep analysis i can see that it got such a bad behaviour.
Could anybody help me to figure the reasons out?
i would appreciate it very much.

Just guys, Take in mind that i'm a total noobies on the field...and that i have never built an amplifier, so my apologies in advance for the stupid questions that i will certaintly make !!!

i'll go ahead with one question....stupid of course....that i have:


should a preamplifier stage have a gain > 1?
i'm wonderinf because from the simulations...This one....has a gain <1 and if i take R22 out of the cicuit, the pre is a unit gain amp....is this normal?

is all the gain on the power amp?


i look forward to receive your good advice
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Old 20th February 2007, 03:25 PM   #2
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this is the simulation's result..
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Old 20th February 2007, 03:29 PM   #3
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sorry....one more question.......super stupid....

is it normal that a preamplifier got a dc componet on the output?
this pre has a certaintly dc-comp.

Of course there gotta be something that i'm doing wrong...because this project is actually working project...and i just tryed to simulate it.....and try to get so a better handle of this tools (simulators...optimizer engines...so on and so forth) and a better handle on amp design....

really hope to learn something new with this 3d.


Thanks in advance.


Best,
Stefano.
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Old 20th February 2007, 04:11 PM   #4
jcx is offline jcx  United States
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1st advice - save line drawings as .png or even .gif not jpeg

2nd the circuit shows a high impedance "current source" output, this needs a resistor load to ground to turn the current into a voltage signal
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Old 20th February 2007, 04:47 PM   #5
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for my own interest... what program do you use to simulate?

thjanks,
patrick
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Old 20th February 2007, 09:23 PM   #6
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i use orcad 10.5 ....


anyways tomorrow i will post the pictures in the format that you suggested me!

i 'm looking forward to receiving other advice on the questions that i raised up.


thanks in advance.
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Old 20th February 2007, 10:51 PM   #7
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Quote:
Originally posted by Stefanoo

i use orcad 10.5 ....


anyways tomorrow i will post the pictures in the format that you suggested me!

i 'm looking forward to receiving other advice on the questions that i raised up.
OrCAD is one of the best.
Drawback is that it cost money.
But this is same for almost every good Sim software.

LTSpice is free, but the library and functions are a bit limited.
At least compared to my Electronics Workbench MultiSim
EWB - http://www.electronicsworkbench.com/

==========================================


Stefanoo.
I recommend you start with some very simple amplifier circuits.
Just to learn how to use simulation features.
Will make it easier to find any problems.

lineup


PS. you can for example try my
Complementary Transistor tester
It will give a hint of your models are good.
There are a lot of BAD MODELS around!. DS.
-------------------------------------
Attachment:
lineup NPN + PNP Transistor tester Circuit
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