Multisim results

[Chandra]

Hi all,

I designed an amplifier circuit for very low currents and so it has to
be extremely accurate. I considered the offset currents and voltages of
the opamp and from the calculations it seems like the circuit is going
to be 0.8% accurate worst case value considering all the temparature
effects. I use Multisim (Electronics Work Bench) for simulations and I
was wondering if there is a way that I could reproduce the same value
of accuracy in multisim results also. Can we change the electrical
parameters like offset voltages and currents of an op-amp in Multisim?
I do not know how well the simulation is going to respond for the
changes in offset currents and voltages. If you have any ideas on how
to do it in Multisim or if there is a better way of validating my
design please let me know. Thank you.

Chandra

[Jerry Avins]

Chandra wrote:
> Hi all,
>
> I designed an amplifier circuit for very low currents and so it has to
> be extremely accurate. I considered the offset currents and voltages of
> the opamp and from the calculations it seems like the circuit is going
> to be 0.8% accurate worst case value considering all the temparature
> effects. I use Multisim (Electronics Work Bench) for simulations and I
> was wondering if there is a way that I could reproduce the same value
> of accuracy in multisim results also. Can we change the electrical
> parameters like offset voltages and currents of an op-amp in Multisim?
> I do not know how well the simulation is going to respond for the
> changes in offset currents and voltages. If you have any ideas on how
> to do it in Multisim or if there is a better way of validating my
> design please let me know. Thank you.

I once programmed a phenolphthalein titration simulation for our high
school's chemistry teacher. When approaching neutrality, the indicator
flashes color with every drop, and that was part of the simulation. The
duration of the flash increased as one gets closer to neutrality, just
as in real life. My "phenolphthalein", however turned green, not red.
When the teacher objected, I told her that it was a reminder to her
students that a simulation's correspondence to reality was not something
that could be relied on.

Electronics Workbench is a fine way to rough out a design. You need to
study the data sheets of all its components to know how your circuit
will drift with time and temperature. Or build a few and measure them.

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Chandra]

That's a good one. Thank you. I guess I was trying to compare the
realistic value that I got thro' data sheets with Multisim value which
isn't that perfect.


Jerry Avins wrote:
> Chandra wrote:
> > Hi all,
> >
> > I designed an amplifier circuit for very low currents and so it has to
> > be extremely accurate. I considered the offset currents and voltages of
> > the opamp and from the calculations it seems like the circuit is going
> > to be 0.8% accurate worst case value considering all the temparature
> > effects. I use Multisim (Electronics Work Bench) for simulations and I
> > was wondering if there is a way that I could reproduce the same value
> > of accuracy in multisim results also. Can we change the electrical
> > parameters like offset voltages and currents of an op-amp in Multisim?
> > I do not know how well the simulation is going to respond for the
> > changes in offset currents and voltages. If you have any ideas on how
> > to do it in Multisim or if there is a better way of validating my
> > design please let me know. Thank you.
>
> I once programmed a phenolphthalein titration simulation for our high
> school's chemistry teacher. When approaching neutrality, the indicator
> flashes color with every drop, and that was part of the simulation. The
> duration of the flash increased as one gets closer to neutrality, just
> as in real life. My "phenolphthalein", however turned green, not red.
> When the teacher objected, I told her that it was a reminder to her
> students that a simulation's correspondence to reality was not something
> that could be relied on.
>
> Electronics Workbench is a fine way to rough out a design. You need to
> study the data sheets of all its components to know how your circuit
> will drift with time and temperature. Or build a few and measure them.
>
> Jerry
> --
> "The rights of the best of men are secured only as the
> rights of the vilest and most abhorrent are protected."
> - Chief Justice Charles Evans Hughes, 1927
> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Chandra]

That's a good one. I guess I was trying to compare the actual value
which I got from data sheets and calculations with Multisim simulation
value which isn't that perfect. Thank you.

Chandra
Jerry Avins wrote:
> Chandra wrote:
> > Hi all,
> >
> > I designed an amplifier circuit for very low currents and so it has to
> > be extremely accurate. I considered the offset currents and voltages of
> > the opamp and from the calculations it seems like the circuit is going
> > to be 0.8% accurate worst case value considering all the temparature
> > effects. I use Multisim (Electronics Work Bench) for simulations and I
> > was wondering if there is a way that I could reproduce the same value
> > of accuracy in multisim results also. Can we change the electrical
> > parameters like offset voltages and currents of an op-amp in Multisim?
> > I do not know how well the simulation is going to respond for the
> > changes in offset currents and voltages. If you have any ideas on how
> > to do it in Multisim or if there is a better way of validating my
> > design please let me know. Thank you.
>
> I once programmed a phenolphthalein titration simulation for our high
> school's chemistry teacher. When approaching neutrality, the indicator
> flashes color with every drop, and that was part of the simulation. The
> duration of the flash increased as one gets closer to neutrality, just
> as in real life. My "phenolphthalein", however turned green, not red.
> When the teacher objected, I told her that it was a reminder to her
> students that a simulation's correspondence to reality was not something
> that could be relied on.
>
> Electronics Workbench is a fine way to rough out a design. You need to
> study the data sheets of all its components to know how your circuit
> will drift with time and temperature. Or build a few and measure them.
>
> Jerry
> --
> "The rights of the best of men are secured only as the
> rights of the vilest and most abhorrent are protected."
> - Chief Justice Charles Evans Hughes, 1927
> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯