variable Vth

Come on, Jason! Read your text, or at least use your head!

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

Drop Vt when you need speed. Raise it when you want to save power (low Vt devices leak like hell).

Hi Keith Thank you for writing in short but with very useful info. Thanks a lot

Jason

Hi Jim

Thanks for the comment. I have read text and used my brain :) I know how Vt affects the performance. But I wish to know more how Vt be varied in application in bulk cmos and soi cmos. How can we make proper changes in certain things that we can control the Vt and would not make the whole systems too complex to be achieved. Thank you all

Jason

Variable in the circuit design, or variable as a processing choice?

...Jim Thompson

Thank you Jim

It will be great if you can share ideas on both domain. Circuit level and also process flow and integration :)

Hear from you and all

Thanks a lot Jason

One can "tune" Vt over a limited range by changing the MOSFET's body voltage. This can be done with active circuitry, or with integrated capacitors to hold a programmable charge (voltage), similar the use in EEPROM cells. It's a specialized technique.

Now there's a vague question for you! What do you mean?

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

That doesn't have anything to do with clock speed.

In general body effects can only be applied to P-channel devices since, in most commercial processes, the N-channel body is the substrate.

But only PhD's would do such a dumb-ass unpredictable thing in the first place ;-)

...Jim Thompson

The Compaq Contura? What operating system did it use? What program told the processor to slow down? How?

VTH doesn't have a fast effect on power consumption.

The only time I've used the effect is for "kick-start" circuits, when normal VTH is reached the kick-start device is "off".

A few processes I've used have had a depletion mode FET... sloppy but useful for starting regulators.

...Jim Thompson

Hello Winfield,

Now I just wish that "modern" laptop designers would understand that general concept. My old Contura could vary its processor clock according to load. The new ones can't and in consequences eat their batteries in under two hours. What a progress.

Regards, Joerg

Hello Jim,

Yes, I know. I just meant the general concept of offering both sides in a trade-off. Lots of power at huge battery drain versus sluggish performance at better battery economy. Kind of like the overdrive button in cars. Old portable computers could do that and it seems most new ones can't.

I am not a chip guy but this variable Vth concept somehow always had that "molasses feel". It wouldn't surprise me it that could make the yield tank because now they'd have to spec two operating modes on one process.

Regards, Joerg

Define "fast".

It's perhaps a useful technique in SOI (the fouth terminal is available to the bold). There are a few patents that teach how to control these things.

Change VB by 0.1V and observe speed change.

Define "useful" ;-)

...Jim Thompson

Hello All

Thanks for discussing I mean how can we actually implement circuit with multiple Vth? How a circuit is control this way?

For integration wise, I refer to process integration between cmos and cmos soi

Hear from you all Thank you

Jason

Hello All

Thanks for discussing I mean how can we actually implement circuit with multiple Vth? How a circuit is control this way?

For integration wise, I refer to process integration between cmos and cmos soi

Hear from you all Thank you

Jason

Joerg skrev:

Isn't that just because you bought a laptop with a regular pentium4 and

not a (more expensive?) pentium4-mobile?

afaik all mobile pentiums and maybe also newer regular pentiums support

"Speedstep" and XP has build in support for it.

-Lasse

Hello Winfield,

Yes, the Compaq Contura. I used DOS and sometimes Windows 3.2 but the latter only when I had to go on the web.

I don't know how it worked in detail but it had a fully static 486, the SL version I believe. These could be used from full to very low clock rates. The programs in those days did not have power save features. IIRC it was the BIOS that did all that. As a user you could select hi-med-lo, plus a variable "on demand" kind of setting which is the one I used. It was done via clicking on some silly dripping faucets but worked fine. Out of curiosity I measured Icc while running SPICE and then again while slowly plugging away on a Word document. Icc dropped to less than half with Word and that was pretty much corroborating the battery runtime. On long flights the folks next to me with their fancy Thinkpads were blown away when theirs quit and I kept writing two hours longer. Especially so because they paid more than twice of what mine cost.

Regards, Joerg