Assistance with Transistor Voltage Amplifier

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

  1. SmokeDarKnight

    Thread Starter New Member

    Dec 2, 2013

    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.

  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    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?
    SmokeDarKnight likes this.
  3. SmokeDarKnight

    Thread Starter New Member

    Dec 2, 2013
    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.

    Thank you for your reply much appreciated.
    Last edited: Dec 2, 2013
  4. WBahn


    Mar 31, 2012
    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.
    SmokeDarKnight likes this.
  5. SmokeDarKnight

    Thread Starter New Member

    Dec 2, 2013
    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
    Ask yourself--Do you want to be an Electronics Engineer,or a "Digital" Engineer?:D

    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!
    SmokeDarKnight likes this.
  7. SmokeDarKnight

    Thread Starter New Member

    Dec 2, 2013
    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 :/