# Assistance with Transistor Voltage Amplifier

Discussion in 'Homework Help' started by SmokeDarKnight, Dec 2, 2013.

1. ### SmokeDarKnight Thread Starter New Member

Dec 2, 2013
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Hello,

I currently in my first stage of a BSC in Electrical & Electronic Engineering course at University and feel like i'm falling at the first hurdle. I completed an HNC in Electrical Engineering at College however this did not include for any Electrical Components.

I've been asked to Design a Two Stage Voltage Amplifier with a gain between 30 and 50. My idea is to Stage each stage one at a time and design 2 stages with a gain of 6 which if i've red the notes correctly is a gain of

Gain Total = Gain Stage 1 . Gain Stage 2 = 6 . 6 = 36

From what i have read the calculations for both stages are identical.

For the Collector Current i have chosen 1mA

My next instruction is to make Ve 10% of Vcc but i cannot find anything in my notes about calculating Vcc.

Am i missing something obvious? Any advice would be much appreciated.

Mike

2. ### Alec_t AAC Fanatic!

Sep 17, 2013
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The calculations will be similar, but not identical. The input impedance of the second stage will have a loading effect on the output of the first stage.
You don't calculate it: it is the supply voltage for the amp, e.g. 9V from a PP3 battery. Perhaps you're thinking of Vc (the collector voltage)? You should choose a collector resistor such that in the amp quiescent state Vc is about half Vcc.
Is the specified gain for DC or AC signals?

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3. ### SmokeDarKnight Thread Starter New Member

Dec 2, 2013
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Hi Alec T

I will take that into consideration. Makes sense thanks. Its only with 10% of my final mark i think i may be putting too much into it if its only with 10%. First Report so not sure what to expect.

Its an AC signal.

Last edited: Dec 2, 2013
4. ### WBahn Moderator

Mar 31, 2012
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5,755
In most places, 10% is basically a letter grade. I don't know what the grades and scaling is like in Scotland. But if it's similar, then it's worth some effort on your part.

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5. ### SmokeDarKnight Thread Starter New Member

Dec 2, 2013
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I'll defiantly try to pass it at least, I have two to do First is Analogue and its the one im struggling with and the other is Digital which i found really easy but i guess the better i do in these the more chance i have in passing the exam.

Saying that however im of the feeling if i don't understand my report then im not going to be ready for the exam. I will most likely stick to the digital section of the exam although im aware there will be a minimum amout of analogue that will take up a chunk of the exam.

6. ### vk6zgo Active Member

Jul 21, 2012
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Ask yourself--Do you want to be an Electronics Engineer,or a "Digital" Engineer?

The other point is that if you don't know the Digital stuff quite as well as you think you do,it may be good to have something to fall back on.

5% for "trying",even if you don't get it right may also be a lifesaver!

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7. ### SmokeDarKnight Thread Starter New Member

Dec 2, 2013
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Hey vk6zgo, i've been asking myself that for a couple of weeks now. My digital report is amazing im so impressed with it, it took me no time at all. I feel secure in digital.

Im going to see how my reports go and the exam and make a decision after that. If things don't goto plan then i will ask for advice from the Uni. Perhaps i would be more suited for a computer based science. Although work is paying me through for the Electrical aspects they might have something else to say about that but i could always start funding it myself. Im already in my 30s and feel like if i give up on education or take a break i'll just mess it up and not return so i want to at least learn something.

If that makes any sense :/