Comparator VS Amplifier

Hi All,

Although it sounds stupid to start such a new topic, I just want to
make clear the difference between them.

comparator: Vout = Vs * sgn( V+ - V- )

amplifier: Vout = gain * ( V+ - V- ) for non-inverting

Are the above correct?

Just interested to know: Is there any IC that contains both comparator
and amplifier? If so, what is the part number? If it requires an
amplifier with bandwidth above 10MHz or even 100MHz, what is the part
number??

Any help would be really appreciated.

Regards,
Will

 

[Jim Thompson]

On 26 Jan 2005 07:38:29 -0800, chickenwing2010@yahoo.com.hk wrote:

Hi All,

Although it sounds stupid to start such a new topic, I just want to
make clear the difference between them.

comparator: Vout = Vs * sgn( V+ - V- )

amplifier: Vout = gain * ( V+ - V- ) for non-inverting

Are the above correct?

Yes.

Just interested to know: Is there any IC that contains both comparator
and amplifier? If so, what is the part number? If it requires an
amplifier with bandwidth above 10MHz or even 100MHz, what is the part
number??

Any help would be really appreciated.

Regards,
Will

I believe that National makes a part that contains one section of an
LM339 and one section of LM324. Search their site.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

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

 

[John Larkin]

On Wed, 26 Jan 2005 08:53:12 -0700, Jim Thompson
<thegreatone@example.com> wrote:

On 26 Jan 2005 07:38:29 -0800, chickenwing2010@yahoo.com.hk wrote:

Hi All,

Although it sounds stupid to start such a new topic, I just want to
make clear the difference between them.

comparator: Vout = Vs * sgn( V+ - V- )

amplifier: Vout = gain * ( V+ - V- ) for non-inverting

Are the above correct?

Yes.


Just interested to know: Is there any IC that contains both comparator
and amplifier? If so, what is the part number? If it requires an
amplifier with bandwidth above 10MHz or even 100MHz, what is the part
number??

Any help would be really appreciated.

Regards,
Will

I believe that National makes a part that contains one section of an
LM339 and one section of LM324. Search their site.

...Jim Thompson

Who said "Never use a comparator as an opamp, and never use an opamp
as a comparator."? Somebody semi-famous, I think.

John

 

[Rene Tschaggelar]

John Larkin wrote:

The best-kept secret around is that LVDS-to-CMOS line receivers make
very fast, cheap comparators.

Just in case, the commonmode range of these is rather small.

Rene

 

[John Larkin]

On Wed, 26 Jan 2005 17:26:40 +0100, Rene Tschaggelar <none@none.net>
wrote:

John Larkin wrote:


The best-kept secret around is that LVDS-to-CMOS line receivers make
very fast, cheap comparators.

Just in case, the commonmode range of these is rather small.

Right. They're usually spec'd for 0.2 to 2.2 or some such; most seem
to work well from a tad below ground to maybe +2.5. The ones we've
tried work nicely comparing against ground.

A nice external-clock-input circuit is a series R, a resonant LC to
ground, and an LVDS receiver. That tolerates all sorts of ringing and
crud on the input.

John

 

[legg]

On Wed, 26 Jan 2005 08:53:12 -0700, Jim Thompson
<thegreatone@example.com> wrote:

I believe that National makes a part that contains one section of an
LM339 and one section of LM324. Search their site.

LM392 is second-sourced by a number of companies.

RL

 

You have to be careful about taking the input of an ECL circuit up to
ground (assuming that you are usuing the standard power supply rails at
0V and -4.5V (or -5.2V, -3.3V or -2.5V or whatever the flavour of the
decade is).

With some ECL IC's this messes up the internal biassing. IIRR one of
the ECLinPS data books had a whole chapter on the subject with a one
page list of parts classified according to what you could get away
with, mainly in the context of what you did with unused inputs.

Needless to say, I can't find it on the web-site

http://www.onsemi.com/site/support/literature/list/0,4456,1161_273,00.html
-----------
Bill Sloman, Nijmegen

 

[Nico Coesel]

John Larkin <jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:

The best-kept secret around is that LVDS-to-CMOS line receivers make
very fast, cheap comparators.

I used to think that too, but take a look at Maxim's site. They have
comparators which are faster, better and cheaper (at least in small
quantities) than LVDS receivers.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

 

[John Larkin]

On Thu, 27 Jan 2005 21:00:51 GMT, nico@puntnl.niks (Nico Coesel)
wrote:

John Larkin <jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:

The best-kept secret around is that LVDS-to-CMOS line receivers make
very fast, cheap comparators.

I used to think that too, but take a look at Maxim's site. They have
comparators which are faster, better and cheaper (at least in small
quantities) than LVDS receivers.

What parts do you refer to? A DS90LV028A dual LVDS receiver has 2.4 ns
max prop delay and costs $1.12, 56 cents per comparator.

We've just almost finished replacing about 2500 defective MAX9690
comparators in units in the field. They fail at high temperature and,
over time, the failure temp drifts steadily down...

John