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vikramts

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Standard Power supply
Mar 31^st, 2005, 9:31am

Hello

I have been using a 15V DC power supply for some op-amp models in my circuit. What values are typically chosen as supply voltages for MOS transistors in commercial applications?I'm not sure if I am justified in using this source. I was supposed to try a 2.5V DC (based on some SPICE models which used the same) but I find that my models function at a higher voltage and not at 2.5V DC.

What is usually chosen for the op-amp so that we can obtain transistor behavior in the best possible region?

Vikram

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Andrew Beckett

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Re: Standard Power supply
Reply #1 - Mar 31^st, 2005, 8:44pm

Well, if it is an IC process, 15V is absolutely not typical - unless you're using some high voltage process. The smaller the geometry, the smaller the supply voltage (as a rule of thumb). A few years back, 5V supplies were commonplace. Then 3V, and for 0.18u and below, 1.8V (although often these type of processes support analog transistors which can be operated at 3V, whereas the digital circuits operate at the lower voltage to reduce power).

From memory of designs I did in the past, 5V supplies were common for (say) 3u to 1u technologies; 3V for 1u to 0.25u; 1.8V below that. That's just a rough idea - actual processes will vary considerably.

So 15V is definitely not typical of most processes!

Even if you have opamps at the board level, I don't think 15V would be typical.

Andrew.

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vikramts

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Re: Standard Power supply
Reply #2 - Apr 1^st, 2005, 9:56pm

well, i just made my models work with a 5v supply and im using 0.8micron...now my transistor model is a level-1 model(was just experimenting with the functionality)...i found that i had convergence problems or blow-ups(current and voltage values too large) for lower supply voltages. since im trying to verify the working of circuits(and not looking for the best possible design for fabrication), is it ok for me to use 5v supply?

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Andrew Beckett Senior Fellow Offline Life, don't talk to me about Life... Posts: 1742 Bracknell, UK	Re: Standard Power supply Reply #3 - Apr 2^nd, 2005, 7:52am It all depends on your models. Presumably your models are intended for use with a particular process and supply voltage. If not, all we can do is guess, given the unknown source of your models. Andrew.
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