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As the picture describes, the Vout is the division's result, but we have an error. Because my experience with MultiSim is not at a high level, why does this happen? Is this my fault ?

[enter image description here]1

ThreePhaseEel
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nikolaosmparoutis
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1 Answers1

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I think your result should be closer to .1V than 1V. The voltage at node 8 is divided by 10 twice Once because of R7 and R8 The opamp circuit divides it by 10 a second time. If you are running a transient analysis, see if you can plot vout as a function of time. It looks likes something is oscillating. Does Multisim assume the complete voltage source with path path to ground if you put 15V for Vcc? In spice, I've always put a voltage source with ground and label to make this connection. Sorry I can't help more.

owg60
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  • problem Solved,i changed the parameters of simulation based on instructions. Now i ve the question ,what Op amp to choose for Vout between -15 +15 and high precision?.Thanks – nikolaosmparoutis Oct 24 '16 at 04:05
  • I would try Analog Devices ADA4522. If you don't have a model fo r this device, look for something with low input offset voltage. How close was the result to 0.1V using the LM107? – owg60 Oct 24 '16 at 20:45
  • the result was more close to theoritical 5 volts: 5.01 Volt with LM107J-14 vs with 5.03 Volts AD711 – nikolaosmparoutis Oct 25 '16 at 02:18
  • BUT the price is more than 80$ for LM107J-14 !!! – nikolaosmparoutis Oct 25 '16 at 02:29
  • For a reason which i do not understand but is good for me with op amp ADA4000 models is at 4.99 Volts ,the same error as LM107 and costs 2.2 $ !!! – nikolaosmparoutis Oct 25 '16 at 02:38