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Original question:

Amplifier for function generator?

LMH6622: Function generator

Nurfatin Basri
Prodigy 20 points
Part Number: LMH6622

Hye, currently i was given task to create a 13.56MHz sine wave synthesizer, as i searched thru the internet, i manage to get a design on creating a function generator for  1MHz using this LMH6622, but mine is 13.56MHz , do you by chance have any idea on design of any function generator using any opamp for that range of frequency? Really need help! Thank you very much in advance!

  • 0
    Guru 140200 points
    Hi Nurfatin,

    can you show the design of your 1MHz sine wave generator?

    I would make the sine wave from a 13.56MHz square wave coming from a quartz oscillator. Connect a RLC low pass filter to the output of this quartz oscillator to form a clean sine wave and amplify this sine wave by a suited OPAmp.

    Kai
  • 0 in reply to kai klaas69
    Prodigy 20 points

    well hello Kai, here is the design that I got,   by the way so you mean i have to make two different circuit is it? one for the quartz , and one for transform from square to sine?? im really sorry, im new to this :( really appreciate ur help ! here is the link to the webpage (  )    www.ti.com/.../snoa839.pdf

  • 0 in reply to Nurfatin Basri
    Guru 140200 points
    Hi Nurfatin,

    this sort of oscillator is nice and simple but not very stable. Amplitude and frequency can vary with temperature and supply voltage. So, if you exactly need 13.56MHz, I would take a ready-made quartz oscillator providing a square wave with exactly this frequency. Drive a 7-pole passive LRC low pass filter with the output of this oscillator and you will get very pure sine wave.

    DDS (Direct Digital Synthesis) circuits often have such a low pass filter at their output. Look for such a circuit and modify the corner frequency to you needs.

    Kai