Issues with resistor value variation

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srivatsan

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Resistor value variation

hi guys,
i have a resistor in my startup circuit. it seems that the value of the resistor after fab will be ±25% or more. (The art of analog Layout and so on). When I simulated with such a deviation. I had a 50% increase in current and 20 decrease in current (appropriately).

Now I wanted to know whether someone who has fabricated a op-amp, has really seen such deviations? If so, what did you do for adjusting the rest of the circuit?

reply. thanks in advance.
srivatsan
 

Re: Resistor value variation

Can you use ion implantation? This will keep the tolerance down. Can you increase the physical size? This will decrease the effects of etching tolerance.
 

Re: Resistor value variation

if the fundry is good, it can control its value of Res. in +-10% or so.
If you want a right value of current, you can trimming the Res.
 

Re: Resistor value variation

I am using MOSIS AMIS C5N run. So, I have no control in choosing a process.

I am not sure about trimming resistors. Is it fabricable in the above process?

Reply. Thanks in advance.

srivatsan
 

Re: Resistor value variation

Dont worry about it.
it is fabricable in the above process.

And you can contact your fundry
 

Resistor value variation

One way is to have some metal contacts for metal change. Trimming is another way and you may need some extra circuits.
 

Re: Resistor value variation

sunking said:
if the fundry is good, it can control its value of Res. in +-10% or so.
If you want a right value of current, you can trimming the Res.
Click to expand...

yeah, I think the best way to get absolutely Res. is trimming.

u can also use Cr-Si as resistor, get a Res. about 10%
 

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