Connect with us

Same component's difference ???? amp,res,cap,tran

Discussion in 'General Electronics Discussion' started by gana, Jul 3, 2013.

Scroll to continue with content
  1. gana

    gana

    6
    0
    Jul 3, 2013
    I have a problem with two amplifiers it generates different outputs, of course tiny difference.

    Why i have a difference where i start?

    questions are?
    1. is there any voltage output differences when i pass voltage through two wires have different length or width or quality?

    2. is there any voltage output differences when i pass voltage through two transistors ?

    3. is there any voltage output differences when i pass voltage through two resistors ?

    4. is there any voltage output differences when i pass voltage through two capacitors polar or not?

    Same component's difference ???? amp,res,cap,tran
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    All components have a spread of possible values. For passive components it is called tolerance and is typically specified as a percentage of the nominal value.

    For other components the specifications may include a range for certain values. For example the gain of a transistor may be specified to be within 80 to 200. So if you pick two at random, you should not be surprised if one had a gain of 120 and the other 160 (say).

    So, each amplifier is made up of different components which will have slightly different values and actual specifications (even if they are within the tolerance)

    In addition, noise will add small, random variations to your signal.

    Part of the design magic is to make a circuit work practically unaffected by changes of this nature (and to minimise noise). In amplifiers, negative feedback can be used to achieve this. However nothing is perfect, and even with all the best design tricks, the use of feedback, etc., there will still remain some small difference. If you're lucky this will be near immeasurable.
     
  3. gana

    gana

    6
    0
    Jul 3, 2013
    Thank you sir

    You mean two same model of transistor? i mean is there any different value between same model and value of transistors.

    Do you mean design magic is kind of method? or just feedback calculation of owner?
     
  4. davenn

    davenn Moderator

    13,833
    1,950
    Sep 5, 2009
    yes the same type of transistor eg a 2N3904 the gain of 2 of them could easily have differen gains, as Steve stated above


    When a GOOD designer of a circuit is working on the design, he will take into account tolerance and gain variations of the various components. He may even put in some variable adjustment so that say... 2 channels of a stereo amplifier will produce a balanced/equal output for a given input when the front panel balance control in in the centre position.

    In another circuit, the designer will make sure that the circuit will always perform as expected ( within design parameters) even when the component values vary a bit will age

    Dave
     
  5. gana

    gana

    6
    0
    Jul 3, 2013
    Thank you sir

    I have recorded my voice in real-time by two preamplifiers they have difference between them.

    But problem is that i expected one of them may generate signal loader than another one but they generate loader and lower alternatively and i am confused how to solve..:eek:

    please take a look this pic:

    [​IMG]

    [​IMG]

    How to solve ?
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    Facebook tells me:

    "The page you requested cannot be displayed at the moment. It may be temporarily unavailable, the link you clicked on may have expired, or you may not have permission to view this page."
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    Showing us the circuit you've used may be a good idea. Those images don't tell me much at all
     
  8. gana

    gana

    6
    0
    Jul 3, 2013
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    One of the interesting features of that circuit is that C4 increases the gain of the stage to close to that of the transistor. Thus, the negative feedback introduced by R5 (predominantly) is effectively countered.

    This is probably the main reason why one has more gain than the other.

    If you have access to a signal source it would be interesting to apply the same signal to each preamp (maybe a few millivolts) and compare the output.

    To fix it you could add a gain control and adjust both so that they have approximately the same gain.
     
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    As Steve and Dave have explained, the gain of that circuit is very dependent on the gain of the transistor, which varies from component to component.

    You can reduce and stabilise the gain of the circuit by adding a resistor in series with C4. Start with a value of about one fiftieth of R4. If the gain is now too low, reduce the value of the new resistor. Or use a preset potentiometer (aka trimpot) so you can adjust the gain.

    You will never get EXACTLY the same signal from the two circuits. If you adjust them for the same gain, you should get something pretty close.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-