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I built the function generator circuit on a breadboard. I applied a signal with an amplitude of 1.06Vpp and a frequency of 5MHz using the DDS 9851 and then sent it to the operational amplifier, AD 8001. After amplification, the signal increased to 4Vpp while maintaining the same 5MHz frequency. However, some distortion appeared in the signal after amplification. To address this, I connected a ferrite bead with a rating of 1kΩ in series with the signal. After using the ferrite bead, the signal became much cleaner with very little noise. This allowed me to remove the large laboratory function generator and apply the amplified signal directly to my sensor.

This is my first experience working with LTSpice software. I recreated the same circuit in LTSpice and did simulation[simulation on LTSPice][1] using the same resistor values and one simulation with more resistors value. However, in the simulation, the signal amplitude did not increase as it did in my real circuit. The signal did not amplify after using the same operational amplifier in LTSpice. Do you think LTSpice should amplify the signal as much as the real circuit does when using a single operational amplifier?

I have drawn a picture of my real circuit, which I will show to you along with the LTSpice circuit and its results. Additionally, I will show you the signal results that I measured with an oscilloscope. Could anyone please share your experience and tell me whether this significant difference in signal amplitude between the real circuit and the LTSpice simulation is common when using simulation software? Or could this discrepancy be due to a mistake on my part, given that there are differences between reality and software simulations? I f there is some mistake on my side, can someone highlight my mistake please

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  • \$\begingroup\$ Did you physically disconnect the function generator from the amplifier? Because it is not possible to get signal output from amplifier if signal input is disconnected. What do you do with the input of the amplifier? Is it floating? \$\endgroup\$
    – sai
    Commented Aug 20 at 2:36
  • \$\begingroup\$ Are you probing the correct node? You don't have your nodes labeled so it's hard to tell. Also, the SINE() voltage waveform accepts the amplitude parameter in peak voltage not in peak-to-peak voltage. So you should enter in 0.53 instead of 1.06. \$\endgroup\$
    – Ste Kulov
    Commented Aug 20 at 3:31
  • \$\begingroup\$ Looks like you are probing the voltage source instead of the op amp output in LTspice. A gain of 7 is to high for an input voltage of 2.12Vpp and +/-6V supply. \$\endgroup\$
    – Raonoke
    Commented Aug 20 at 8:28
  • \$\begingroup\$ Sai--- Thanks for the reply. \$\endgroup\$ Commented Aug 20 at 17:13
  • \$\begingroup\$ Sai-I used the module AD 9851 DDS to generate the signal and connect it to non inverting pin of Operational amplifier. I didn't disconnect the DDS signal to the input of operational amplifier. the signal at the input of operational amplifier is 1.06 Vpp. At the output of the signal the signal is 4Vpp with usage of feedback resistors. the problem is in Simulation of LTSPice, as i build the same real circuit in LTSPice but the operational output doesn't increase like the one increase in real circuit on the breadboard \$\endgroup\$ Commented Aug 20 at 17:22

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