Amplification of two sinusoidal signals

Discussion in 'Homework Help' started by Citro, Apr 13, 2013.

  1. Citro

    Thread Starter New Member

    Apr 13, 2013
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    Hello all
    Could anybody help me with task.
    I have two sinusoidal signals, phases difference is 90 degrees, frequency about 500kHz, wires from source of signal to PCB are about 15 cm. Amplitude of signals are about 300mV.
    I have to use operational amplifiers to get the output 1V. Phase difference should be the same after amplification.
    P.s. I have prototyping PCB, and I am going to buy some OpAmp in DIP case.
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Show your work, and tell us what you are stuck on.
     
  3. #12

    Expert

    Nov 30, 2010
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    A plastic, plug-in, practice board is going to give you trouble with stray capacitance at 500 KHz. I hope, "prototyping PCB" means copper traces and solder.
     
  4. Citro

    Thread Starter New Member

    Apr 13, 2013
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    if I change frequency to 100 kHz?
    And what i need to do if i have Power Supply with only +5V, without -5V.

    that's what I got in the simulator
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    How much gain does your amplifier need? How much do you have in your simulation?
    Show us calculations. Anyone can use a simulator.
     
  6. Sue_AF6LJ

    Member

    Mar 16, 2013
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    Op-Amps seem like overkill.
    You could do the same with a single stage transistor amplifier.
    If you use common emitter stages the output will be inverted but they will still be 90 degrees apart (in quadrature to each other)

    You could also use common base amplifiers if your source can handle a low impedance load.
     
  7. vk6zgo

    Active Member

    Jul 21, 2012
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    Hi Sue,great to see you on this forum.
    Your commonsense approach to Electronics will go over well here!

    73,VK6ZGO
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    This is the homework forum. The OP said
    .
    I assumed this was part of the assignment.
     
  9. Citro

    Thread Starter New Member

    Apr 13, 2013
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    If 300mV need increase to 1V. I think, gain must be about 3.3.

    I made new simulations.

    With MCP601 (rail to rail OP-amp)

    In case 1.jpg, 1s.jpg, I tried to make a differential amplifier at 3 OP-amp.

    In case 2.jpg, 2s.jpg I tried to make a differential amplifier at 3 OP-amp.

    Please advise me which case is better, and where will be better use Adjustable resistors for adjust gain.

    All resistors in both cases were selected randomly. I just picked them up to get the desired gain.
     
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  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    You are correct about the gain. Your circuits are unnecessarily complicated. You don't need a differential amplifier.

    1. Have you been taught feedback theory, and/or op amp circuits?

    2. Do you know anything about the signal source? What is the source impedance, or what is the signal coming from?

    3. Are the two signals separate, or are they combined on the same wire?

    Please answer ALL the questions.
     
  11. Citro

    Thread Starter New Member

    Apr 13, 2013
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    1.Yes
    2.Source of signals is phototransistor, but i don't know kind of it, and don't know impedance.
    3. Actually i have four wire, 1 and 2 sinusoidal signal and inverse sinusoidal signal, 3 and 4 sinusoidal signal and inverse sinusoidal signal.

    I'd like use diff. op. amp because I want to avoid interference
     
  12. WBahn

    Moderator

    Mar 31, 2012
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    When you say "inverse sinudoidal signal", do you mean that if you measure between that line and ground that you see a sinusoid? Or do you just mean that it is the return wire for that signal?

    If the former, is your 300mV the peak value of the sinusoid on either line, or the peak value of the difference between the two lines?
     
  13. Citro

    Thread Starter New Member

    Apr 13, 2013
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    I mean measure between line and ground. 300mV is peak value of sinusoid on either line.
     
  14. WBahn

    Moderator

    Mar 31, 2012
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    So you have 600mV peak value between them?

    And what are you wanting for an output? A singal-ended output in which you have a 1V amplitude signal relative to ground? Or a differential output in which you have a 1V amplitude signal between the two outputs? Or what?
     
  15. Citro

    Thread Starter New Member

    Apr 13, 2013
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    Sorry, i have 300mV peak.

    I'd like will get 1V amplitude signal relative to ground.
     
  16. Sue_AF6LJ

    Member

    Mar 16, 2013
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    I'll have to pay more attention to the forums I post in...
    Sorry. :)
     
  17. WBahn

    Moderator

    Mar 31, 2012
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    It's the kind of mistake that if we haven't made it, will will. And if we have made it, we will make it again.
     
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