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AC input to bridge

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ronv

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I'm chasing a problem around in spice (I think). I would like to remove R1, C2 and U6 from the attached schematic, but when I do the op amps don't like the negitive voltage comming from the bridge supply. The plots show a negitive sine wave even though the voltage source is set to 0 to 35. If I add a small positive offset to the voltage source all is well.
 

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Is this just a simulator problem? Is the simulator giving an error and saying that there is a negative supply on the op amp? In real life that won't happen as there is nothing that can supply negative current.

I assume that source V1 is supposed to represent a mains transformer. I hope that it is a relative voltage between points V1 and V2, not absolute voltages. In fact, the sinewaves shown on the simulator are far from what you would see with an oscilloscope, because the absolute voltage on V1 and V2 is only controlled by the bridge rectifier near the peaks of voltage. At all other times the voltages can float anywhere in the 0 - 35 V range. Small stray current paths and stray capacitances will mean that the waveform is far from what the simulator shows.

You could just assume that a bridge rectifier works and simulate the supply as DC with a bit of 120Hz ripple.
 
Yes, I think it is just the simulator but it is nice to be able to see that the ripple voltage is ok for the regulator design without having to calculate it. Spice doesn't tell me it is the reverse voltage it just time steps out, but it shows enough that you can see the op amps glitch and see the negitive current thru them. I thought maybe there was a better way to do the input to the bridge but every schematic I see uses a similar input.
 
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