I'm making a super simple spice sim with ltspice for a noninverting opamp with a gain of 10, and the simulation doesn't give the expected results with the resistors values calculated.
For the gain of 10, if the resistor going from in to ground (R1) is a 10k, then calculations say the feedback resistor (Rfb) should be 90k. Normal, with a gain of 1+Rfb/R1, should be exactly 10.
That is what I tried in sims, and it doesn't set the gain at 10.
To obtain that gain of 10, I tweaked the feedback resistor to get very close to the wanted gain of 10, and that required a feedback resistor value of 95k1625, which obviously isn't quite like the 90k as calculated.
Why? This shouldn't happen. The opamp used in the sim is the TL071, so with the JFET inputs very high impedance, input currents shouldn't cause any noticeable interference in the gain.
Is the sim wrong and it can't get this right? Or I am missing something else?
For the gain of 10, if the resistor going from in to ground (R1) is a 10k, then calculations say the feedback resistor (Rfb) should be 90k. Normal, with a gain of 1+Rfb/R1, should be exactly 10.
That is what I tried in sims, and it doesn't set the gain at 10.
To obtain that gain of 10, I tweaked the feedback resistor to get very close to the wanted gain of 10, and that required a feedback resistor value of 95k1625, which obviously isn't quite like the 90k as calculated.
Why? This shouldn't happen. The opamp used in the sim is the TL071, so with the JFET inputs very high impedance, input currents shouldn't cause any noticeable interference in the gain.
Is the sim wrong and it can't get this right? Or I am missing something else?
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