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100kHz sine wave oscillator

Heimo Gaicher27
Prodigy 40 points
Other Parts Discussed in Thread: LM358

Hello!

I want to create an easy 100kHz sinus oidal signal with an amplitude of 10V (20Vss). Input voltage = 24VDC.

The circuit should be able to deliver 50mA. A good distortion is not very importent in this case.

Can anybody recommend a reference design?

Many thank's

  • 0
    TI__Prodigy 670 points

    Hello Heimo,

    Please see this app note for a design you can use to build a Sine Wave Generator. I have also attached the Excel calculator referenced in the document you can use to compute passive values.

    You should try to select an OpAmp that have a BW 10x of the frequency want to generate.

    Kind Regards,

    Dylan Bartlett

    0638.SNOA839.xls 

  • 0 in reply to D_Bartlett
    Prodigy 40 points

    Hello Dylan,

    many thank's for your information! Based of the schematic i hade done a simulation with LTSpice.

    For 100kHz i used a LM358 as opamp and i calculated: R1= 7215Ohm, R5=R6= 1125Ohm. For C1 i select a 1nF capacitor. In this case C2 = 1nF and C3 = 2nF.

    In my simulation i got a sinosoidal signal with an amplitude of 4.8V (Vcc=6V). But the frequency of the signal is just 38kHz!

    Can you give me a hint why the frequency is only 38kHz?

    Kind Regards

    Heimo

  • 0 in reply to Heimo Gaicher27
    TI__Guru 63700 points

    Heimo,

    Looking at your generated waveform you may clearly see it is grossly distorted due to slew limitation. To avoid this, you need to pick an op amp with minimum slew rate of: SR=2*Pi*f*A which in your case means 6.28V/us. In order to assure this over process variation, you need to use an op amp with typical slew rate of 10V/us.