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Frequency amplification

  1. May 20, 2016 #1
    How do I know, how big of a voltage gain for an amplifier do I need, if I want to increase the input frequency from 250 Hz to 50 kHz?
    Thank you.
  2. jcsd
  3. May 20, 2016 #2


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    Without knowing the details of your circuit I don't think we can help you.
  4. May 20, 2016 #3
    The purpose any amplifier is to use a small voltage signal as an input and generate a higher voltage signal with the same waveform.
    Generally transistors are used for this but transistors vary in their optimum operating voltage range, and they also vary for input sensitivity.
    Transistors which can guarantee to efficiently/accurately amplify higher frequency input signals tend to be harder to make, and at very high frequencies they get expensive.
  5. May 20, 2016 #4


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    It is very unlikely that you would be building a circuit to do what you seem to be saying. Perhaps you could explain what you would like to achieve, then we can tell you how to go about it?
  6. May 20, 2016 #5


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    Not making any sense. Voltage gain does not increase frequency.
  7. May 21, 2016 #6
    Ok, I want to increase the frequency of an audio source from 250 Hz to 50 kHz so I can hear it via inner ear...Roughly speaking...
  8. May 21, 2016 #7
    There isn`t a circuit yet, because I don`t have nearly enough knowledge to build one yet, that`s why I want to know, how to go about it. I simply want to increase the frequency of an audio source from 250 Hz to 50 kHz so I can work with ultrasound, listen to it by using my inner ear.
  9. May 21, 2016 #8
    Not going to argue, that`s why I`m here- to learn!
  10. May 21, 2016 #9
    Do you want to increase frequency/amplitude?
  11. May 21, 2016 #10
    Yes, just that-frequency.
  12. May 21, 2016 #11
    Then there are something called as frequency multipliers
  13. May 21, 2016 #12
    Thank you for the intel, any suggestions for one that would be relatively cheap and amplify the frequency 200x?
  14. May 21, 2016 #13
    Yes, they are verily possible. We can double or triple frequency using some simple circuits. The doubled or tripled frequency signals can be used for various applications.
    Take the case of microprocessors. A faster clock frequency(say twice or four times) means faster operation in sequential circuits.
    But it is not much use of increasing frequency by 200 times( either for sine or square eaves).
    Instead of increasing frequency from 250 Hz to 50Khz, you can generate 50KHz output itself.
  15. May 21, 2016 #14


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    The amplifier does not need a different gain for a different frequency. It needs a greater passband. Audio power amplifiers often have an ultrasonic filter to prevent parasitic oscillation in the output stage. That may block your 50kHz.

    What type of transducer will you use? What is the frequency response?
    To compensate for the frequency response of the transducer may need to change amplifier gain.

    With 50kHz you will probably feel very irritated, but you will not perceive it as a sound.
    How good were your ears. If you are not very careful you will probably damage your ears in the experiment.
  16. May 21, 2016 #15
    I do have a 50 kHz square wave generator, it would be possible to mix it with the audio source, but what would happen to the frequency of the mixed signal?
  17. May 21, 2016 #16
    But, can we really hear 50Khz? Is 20Khz, not the maximum frequency we can hear?
  18. May 21, 2016 #17
    That would be the tramsducer I have in mind, the inner ear should be able to perceive it as sound...I`m positive there is a way of getting this done and I will do so no matter how many people I have to ask for help...
  19. May 21, 2016 #18
    What do you mean by the term "mixing"? does it mean voltage addition(adding function generator waveform and audio signal)?
  20. May 21, 2016 #19
    You are correct, but the inner ear is something we have in common with dolphins and a few other species who can perceive ultrasound, so it should be possible.
  21. May 21, 2016 #20
    No, I meant by using an audio mixer of sorts to combine the two signals and create a third one, just that the third frequency most likely won`t be at 50 kHz.
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