boost function generator output

Discussion in 'The Projects Forum' started by roadey_carl, Jan 22, 2012.

  1. roadey_carl

    Thread Starter Active Member

    Jun 5, 2009
    116
    5
    Hello everybody, hope your all well.

    I've recently brought some more electronics equipment including a rigol DS1052E 50mhz oscilloscope and a vector 2002 2Mhz function generator.

    I'd like to boost the output of the function generator current and voltage if passable.... I was messing around with some transistors and I could boost it around 200mA but only 1 side of any wave form because the other was at ground.

    I measured the short circuit output at 10v and got just under 110mA. Id like to be able to add an external PSU to power the circuit, 1-60vdc at about 1A, maybe a bit more if passable, I need it to be able to output 5-500Khz?

    Could anybody recommend a amplifier capable of doing this?

    here is a link for the spec of the function generator :
    http://www.gainexpress.com/product_info.php?products_id=836&osCsid=aqbegvc8elhaov38rhd60me6j2

    Thanks for your brains!
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    A function generator can output positive and negative voltages. You will need a dual supply plus an amplifier. The amplifier can be an op-amp preamplifier (for voltage amplification) and a push-pull transistor pair driven by the op-amp to boost current.
     
  3. PaulEE

    Member

    Dec 23, 2011
    423
    32
    To bring the above post "home", take a look at something like the LM3886 class AB audio amplifier chip. It is exactly what is described above and all in one package.

    Just get yourself (or build yourself) a nice split supply, hook up the LM3886, and off you go.
     
  4. roadey_carl

    Thread Starter Active Member

    Jun 5, 2009
    116
    5
    Sweet! Thanks a lot, I'll google it when I get home! :eek:)
     
  5. roadey_carl

    Thread Starter Active Member

    Jun 5, 2009
    116
    5
    I've just been looking at the datasheet for the lm3886. Im not quite sure how I would attach the wave input... would it be similar to the test circuit 2?
     
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Are you sure it can operate satisfactorily at frequencies above 20kHz?
     
  7. roadey_carl

    Thread Starter Active Member

    Jun 5, 2009
    116
    5
    Hi again,

    I brought a TDA2050 audio amplifier but I'm not to sure how to set it up. Id like to connect my sine wave output from a function generator to the input.

    Theres a couple of things I'm not so sure of and was hoping someone could help?

    1: the dual PSU. is the ground where C7 and the speaker is connected to?
    the positive to the IC is pin 5 + and negative pin 3 - ?
    2: would I connect my input from the function generator to the inverting and non-inverting input? and this will pick up both the positive and negative cycle?

    I'm using the circuit on page 4 of the attached PDF.
    http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1461.pdf

    Thanks again.
     
  8. PaulEE

    Member

    Dec 23, 2011
    423
    32
    Good call. I didn't see the 20 kHz to 200 kHz spec.

    It can, but the peak-to-peak output is limited to around 10 Vpp.

    High frequency and high amplitude start to add to price with op-amps - in my experience, anyway.

    As far as the chip you ended up getting...

    I think it's going to get distorted approaching 100 kHz, or, at least, the amplitude will start to go down. This will be most noticeable at high frequencies or high peak-to-peak switching, as in square waves.

    Answer to #1: Yes, yes, and yes. All the leads that terminate with a horizontal line, like those on the speaker, that cap, etc..are ground.

    Answer to #2: You'd hook up the input of the generator between "Vin" and ground.
     
    Last edited: Feb 6, 2012
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