variable Vth

J

jason

Guest
Hello All

Could anyone tell me why cmos circuit with variable Vth is considered
an advantage for low power technology?

Kindly advise.
Thank you

best regards
Jason
 
In article <1124461190.915781.254350@f14g2000cwb.googlegroups.com>,
cheanglong@gmail.com says...
Hello All

Could anyone tell me why cmos circuit with variable Vth is considered
an advantage for low power technology?
Click to expand...
Drop Vt when you need speed. Raise it when you want to save power (low
Vt devices leak like hell).

--
Keith
 
On 19 Aug 2005 07:19:51 -0700, "jason" <cheanglong@gmail.com> wrote:

Hello All

Could anyone tell me why cmos circuit with variable Vth is considered
an advantage for low power technology?

Kindly advise.
Thank you

best regards
Jason
Click to expand...
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 |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
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
 
On 20 Aug 2005 01:11:10 -0700, "jason" <cheanglong@gmail.com> wrote:

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.
Click to expand...
Variable in the circuit design, or variable as a processing choice?

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
Click to expand...

...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 |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
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
 
jason wrote...
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 without making the whole system too complex...
Click to expand...
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.


--
Thanks,
- Win
 
On 21 Aug 2005 05:40:04 -0700, "jason" <cheanglong@gmail.com> wrote:

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
Click to expand...
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 |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Hello Winfield,

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.
Click to expand...
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

http://www.analogconsultants.com
 
On Sun, 21 Aug 2005 21:09:22 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Winfield,

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 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

http://www.analogconsultants.com
Click to expand...
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
--
| 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 |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Joerg wrote...
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.
Click to expand...
The Compaq Contura? What operating system did it use?
What program told the processor to slow down? How?


--
Thanks,
- Win
 
Hello Jim,

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.

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.
Click to expand...
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.

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

http://www.analogconsultants.com
 
On Sun, 21 Aug 2005 22:17:59 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

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.

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.

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.

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

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

http://www.analogconsultants.com
Click to expand...
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
--
| 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 |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Sun, 21 Aug 2005 16:58:43 -0700, Jim Thompson wrote:

On Sun, 21 Aug 2005 22:17:59 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

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.

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.

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.

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

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

http://www.analogconsultants.com

VTH doesn't have a fast effect on power consumption.
Click to expand...
Define "fast".

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.
Click to expand...
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.

--
Keith
 
On Sun, 21 Aug 2005 22:46:02 -0400, keith <krw@att.bizzzz> wrote:

On Sun, 21 Aug 2005 16:58:43 -0700, Jim Thompson wrote:

[snip]

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

[snip]

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

Define "fast".
Click to expand...
Change VB by 0.1V and observe speed change.

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.

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.
Click to expand...
Define "useful" ;-)

...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 |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
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:

Hello Winfield,

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 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

http://www.analogconsultants.com
Click to expand...
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,

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.

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

http://www.analogconsultants.com
 
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