10Khz-500Mhz Amplifier

Discussion in 'General Electronics Chat' started by radetonator, Dec 20, 2011.

  1. radetonator

    Thread Starter Member

    Aug 1, 2011
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    I plan to build a signal amplifier for piezoelectric sensor. The gain should be 35dB and the frequency range is 10kHz - 500Mhz. What amp should be used?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Here you go:
    http://www.minicircuits.com/MCLStore/ModelInfoDisplay?13244209462760.9486691670660741
    $80/ea, buy two of them and connect them in series. 10kHz to 1000MHz, 17dB+17dB = 34dB.
    The input to the amplifiers can be up to +5dB with no damage; and they can output up to +9dB. So, you need to ensure that the input to the 1st amp cannot go above -12dB.

    Trying to build a broadband amplifier yourself will be a long and trying process.
     
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  3. radetonator

    Thread Starter Member

    Aug 1, 2011
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    so cool. could you recommend some broadband amps from TI NS or ADI?:)
     
  4. radetonator

    Thread Starter Member

    Aug 1, 2011
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  5. SgtWookie

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    Jul 17, 2007
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    Last edited: Dec 20, 2011
  6. SgtWookie

    Expert

    Jul 17, 2007
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    This is why I'm encouraging you to buy something off-the shelf.

    The fastest opamp National Semiconductor has is the LMH6703; it's -3Db bandwidth is 1.2 GHz. With only a gain of 2, it's -3dB point is 750 MHz. You would have to cascade 5 of them at a gain of 2.0362 to get to 35dB, and your S/N ratio would go out the window.

    Analog Devices has the AD8000 @ 1.6GHz, but you'd have to cascade those as well.

    I don't know if you're wanting to look at the build aspect for want of a project, or trying to save money.

    Unless you have a network analyzer, or at least a spectrum analyzer and a signal generator that can sweep past 500MHz, it'll be mighty tough to make progress.

    Circuits that operate in the 50MHz and under range are fairly easy. When you're in the 500MHz range, things start to look more like magic than electronics. A multilayer 0805 ceramic cap that measures 47pF in the 10mHz range will look like 160pF at 500MHz just due to the parasitics. A short straight piece of wire becomes an inductor that looks like a brick wall to your signal.

    Even if the above opamps can be had for say, $4.00/ea or less, that's just the beginning. Depending on how much experience you have, and test equipment on hand the project could take many months. I'm afraid I just don't have the time and patience to take on a project like that for one person.

    The MiniCircuits solution is really a bargain for what it'll do for you, and you could put it to use practically as soon as you received it.
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I'm amazed they are selling an amp with that bandwidth so cheaply!

    As Wookie stated, once you get past about 300Mhz, and especially past 500Mhz, Circuit layout and board design becomes an art based on science. Trace widths and inter-trace spacing, as well as board thickness all have different rules, which are often mutually exclusive from 1Mhz to 1Ghz, they managed it somehow, but not with much gain. Parasitic Impedance (capacitance and inductance) which are small enough to be negligible at most project speeds are suddenly major obstacles when dealing at those frequencies.

    Seriously, even if you got all the parts for free, I doubt you'd get a working circuit board the first time. Usually at least 4 layers are needed, and electricity takes on some traits of light.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Isn't it incredible?

    I don't know of anywhere else you can buy neat little (they ARE small!) modules like that with anywhere near that performance without spending several times that much.

    We used lots of these Mini-Circuits modules in R&D. You could put together most of a system pretty quickly with them.
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    If you hadn't stated that site is on the up and up, I wouldn't have believed the price, honestly.

    I hope those are only used for good purposes in bands the user owns or has rights to.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Well, they're pretty low power out; +9dB is max. There are other models they make which have lots more output power.

    The FCC has been really cracking down on illegal use of transmitters (wrong frequency, too much power, etc.) It doesn't take them long at all to track down someone causing problems. You just don't want to get on their bad side.
     
  11. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    A piezo sensor that works from 10kHz to 500MHz? Should that read 10kHz to 500kHz?
     
  12. radetonator

    Thread Starter Member

    Aug 1, 2011
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    yes, it's 500Mhz.
    PVDF sensor to detect ultrasonic signal
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Do you have the datasheet for this piezo sensor?
    A link or uploaded would be helpfull.

    Bertus
     
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