Save big on an advanced USB-connected I/O module

[David Novak-2]

We're selling an Expert I/O 1000 on Ebay with a starting price of only
$240. That's a savings of $739!

Full details for the module are available at
http://www.dajac.com/expert_io.html.

The Ebay listing is at
http://cgi.ebay.com/USB-I-O-Data-Acquisition-DAQ-Control-Module_W0QQitemZ250419404927QQcmdZViewItemQQptZBI_Control_Systems_PLCs?hash=item3a4e28e07f&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

Best Regards,
David

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[Xiaofan Chen]

On Fri, May 8, 2009 at 5:50 AM, David Novak <David.Novak@...> wrote:
> We're selling an Expert I/O 1000 on Ebay with a starting price of only
> $240. That's a savings of $739!
>
> Full details for the module are available at
> http://www.dajac.com/expert_io.html.

Looks nice. Not many I/Os have push-pull output even though now
universal digital input (source/sink) are more and more common.

By the way, what is the push-pull IC you are using? I am also
trying to find out similar push-pull output ICs. Last time I
used one from Germany company IC-Haus (similar to iC-GF:
http://www.ichaus.de/news.php?nid=63). But it is too complicated
for my current intended application.


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[solarwind]

On Sat, May 9, 2009 at 11:27 PM, Xiaofan Chen <xiaofanc@...> wrote:
> Looks nice. Not many I/Os have push-pull output even though now
> universal digital input (source/sink) are more and more common.
>
> By the way, what is the push-pull IC you are using? I am also
> trying to find out similar push-pull output ICs. Last time I
> used one from Germany company IC-Haus (similar to iC-GF:
> http://www.ichaus.de/news.php?nid=63). But it is too complicated
> for my current intended application.

What's push-pull?
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[Vitaliy-2]

solarwind wrote:

> On Sat, May 9, 2009 at 11:27 PM, Xiaofan Chen <xiaofanc@...> wrote:
>> Looks nice. Not many I/Os have push-pull output even though now
>> universal digital input (source/sink) are more and more common.
>>
>> By the way, what is the push-pull IC you are using? I am also
>> trying to find out similar push-pull output ICs. Last time I
>> used one from Germany company IC-Haus (similar to iC-GF:
>> http://www.ichaus.de/news.php?nid=63). But it is too complicated
>> for my current intended application.
>
> What's push-pull?

http://en.wikipedia.org/wiki/Push%E2%80%93pull_output
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[Olin Lathrop]

solarwind wrote:
>> By the way, what is the push-pull IC you are using? I am also
>> trying to find out similar push-pull output ICs. ...
>
> What's push-pull?

Misnamed "totem pole" in this context.  What he is referring to is the
ability of the IC to actively drive its outputs both high and low.
Sometimes outputs can only drive one way, usually low, with a passive pullup
making the line float high when nothing is driving it low.  Sometimes the
pullup is integrated into the IC, sometimes not.  This type of active low
and passive high output is referred to as "open drain" when implemented with
FETs and "open collector" when implemented with bipolar transistors.

Totem pole outputs are good for driving a digital line where all other nodes
on the line are inputs.  They can produce fast and sharp edges in both
directions.  Open drain outputs can be useful on busses when different nodes
could be driving a line at the same time.  The line will be high when no
output is driving it and low when one or more are driving it.  No harm or
excessive current results when two outputs try to drive the bus to opposite
states, unlike with totem pole outputs.

As for "push pull", this refers to two stages driving in the same
directional alternately.  This was a common topology for the final stage of
audio amplifiers using tubes.  Tubes are sortof like N channel FETs with no
such thing as a P channel equivalent.  The final stage was often into a
transformer with the center tap of the primary to power and the two ends
each to their own plate (drain) of a tube.  The two tubes would be driven on
alternate polarity of the output waveform.  Hopefully you can see this is
quite different from a totem pole output.


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[Xiaofan Chen]

On Sun, May 10, 2009 at 8:54 PM, Olin Lathrop <olin_piclist@...> wrote:
> solarwind wrote:
>>> By the way, what is the push-pull IC you are using? I am also
>>> trying to find out similar push-pull output ICs. ...
>>
>> What's push-pull?
>
> Misnamed "totem pole" in this context.

Apparently you are in a different line than automation.
Here we typically talk about sink input/output and source
input/output.
http://www.automationdirect.com/static/specs/sinksource.pdf

A push-pull (or universal) output can do both sink/source
An universal input is can both sink/source.

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[Vitaliy-2]

Olin Lathrop wrote in "[AD] Save big on an advanced USB-..":
>>> By the way, what is the push-pull IC you are using? I am also
>>> trying to find out similar push-pull output ICs. ...
>>
>> What's push-pull?
>
> Misnamed "totem pole" in this context.  What he is referring to is the
> ability of the IC to actively drive its outputs both high and low.

[snip]

> As for "push pull", this refers to two stages driving in the same
> directional alternately.

"Totem pole" and "push-pull" both mean the same thing.

=====
Wikipedia: Totem pole (disambiguation)
Totem pole output, also known as a push-pull output, a type of electronic
circuit

http://en.wikipedia.org/wiki/Totem_pole_output
=====

Take a look at this circuit:

http://upload.wikimedia.org/wikipedia/en/7/72/Electronic_Amplifier_Push-pull.png

It's easy to see that the push-pull can actively drive the output in both
directions (HIGH and LOW).

Vitaliy

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On Sun, 10 May 2009 15:42:19 -0700
"Vitaliy" <spam@...> wrote:

> "Totem pole" and "push-pull" both mean the same thing.

Not necessarily. CMOS outputs are generally push-pull. They have a
P-channel FET above and an N-channel fet below. Both are in digital model
(on/off). 'Totem-pole' will never apply to a CMOS output.

TTL and such have above and below NPN transistors. The lower is really
working in digital mode. The upper NPN is in linear mode, and mainly
serves as an active resistor. There's almost always a diode between both
transistors, which is part of the totem pole output, to protect the upper
transistor, which doesn't even like to go all the way to VCC.

Wikipedia is wrong there... That happens.

John
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[Olin Lathrop]

Xiaofan Chen wrote:
>> Misnamed "totem pole" in this context.
>
> Apparently you are in a different line than automation.
> Here we typically talk about sink input/output and source
> input/output.

Saying that a output can sink and/or source is fine.  I was pointing out
that "push pull" is not the correct term.


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[Olin Lathrop]

Vitaliy wrote:
> Take a look at this circuit:
>
> http://upload.wikimedia.org/wikipedia/en/7/72/Electronic_Amplifier_Push-pull.png
>
> It's easy to see that the push-pull can actively drive the output in
> both directions (HIGH and LOW).

Only if you believe the author's claim that this really should be called
"push pull".  Apparently that term has gotten misused since its original
meaning, and that misuse has stuck in at least a few places.  I guess it's a
handy term that seems to be applicable, especially for those that never
learned its original definition.


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[ivp]

>> "Totem pole" and "push-pull" both mean the same thing.
>
> Not necessarily

> Wikipedia is wrong there... That happens.

To be fair, the entry does say what you said, and what I understood to
be the difference -

A special configuration of push-pull, though in fact an exception, are
the outputs of TTL and related families. The upper transistor is functioning
as a active pull-up, in linear mode, while the lower transistor works
digitally.
For this reason they aren't capable of supplying as much current as they
can sink (typically 20 times less). Because of the way these circuits are
drawn schematically, with two transistors stacked vertically, normally with
a protection diode in between, they are called "totem pole" outputs

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On Mon, 11 May 2009 12:24:23 +1200
Jinx <joecolquitt@...> wrote:

> To be fair, the entry does say what you said, and what I understood to
> be the difference -

Yes... That is the modification I just made to the Wikipedia, ;-) Check
history at:

http://en.wikipedia.org/w/index.php?title=Push–pull_output&action=history

John
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[Vitaliy-2]

Olin Lathrop wrote:

>> Take a look at this circuit:
>>
>> http://upload.wikimedia.org/wikipedia/en/7/72/Electronic_Amplifier_Push-pull.png
>>
>> It's easy to see that the push-pull can actively drive the output in
>> both directions (HIGH and LOW).
>
> Only if you believe the author's claim that this really should be called
> "push pull".  Apparently that term has gotten misused since its original
> meaning, and that misuse has stuck in at least a few places.  I guess it's
> a
> handy term that seems to be applicable, especially for those that never
> learned its original definition.

You mean, the original definition from the pre-transistor era? Perhaps your
definition needs to be updated? :) The meaning of words can change over
time.

-->FWIW, in Russian this type of circuit that has pnp/npn or
N-channel/P-channes FETs, is called "pushpul'nyi kaskad" (lit. "push-pull
cascade").

The name in this situation, makes total sense: the output is "pushed" by one
transistor, then it's "pulled" by the other one.

Vitaliy

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[Bob Blick-4]

Vitaliy wrote:

> "Totem pole" and "push-pull" both mean the same thing.

Personally I think totem pole is one implementation of push-pull, since
push-pull can be done many ways.

Digi-key assigns totem pole and push-pull to Microchip's TC54:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556197&keywords=tc54

Looking at Microchip's datasheet, they specify push-pull and
complementary but do not mention totem pole. To me totem pole suggests
the TTL implementation using NPN transistors, not complementary. But I
am not fixed on that definition, if I saw totem pole in a description I
would want clarification of the topology if it was important to me.

I think a lot of reference information is written by people who do not
have a complete grasp of the difference between a principle and an
implementation of the principle.

Cheerful regards,

Bob
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[ivp]

>> To be fair, the entry does say what you said, and what I understood
>> to be the difference -
>
> Yes... That is the modification I just made to the Wikipedia, ;-)

That's an awfully convenient explanation ;-)))

So often people complain about all manner of things in life but do
nothing to correct it

Good for you
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[ivp]

> Personally I think totem pole is one implementation of push-pull,
> since push-pull can be done many ways.

To me, it seems totem pole is more like the open collector (RA4)
on many PICs. The low-side transistor is a digital switch for sinking
current, whereas the user-added pull-up/high-side resistor allows
only limited "pushing" or sourcing of Vcc current through it
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[Alan B. Pearce-2]

>"Totem pole" and "push-pull" both mean the same thing.

Not historically. I am with Olin on this one, but see below ...

Push-pull output has historically been used for valve and transistor
amplifiers that have an output transformer with centre tapped primary, each
half driven alternatively in a Class B configuration. This was the
configuration of output stage that every 6 transistor pocket radio from the
50s through the 70s used.

Totem pole has historically been the term used for the likes of TTL logic
output stages. These devices never used the term push-pull in their
descriptions from the manufacturer.

Possibly there has been some confusion arise through the use of push-pull
for transformerless transistor output stages in audio amplifiers, which
although of a totem pole style circuit configuration, used the term
push-pull.

So from this one ends up using push-pull for linear use, and totem pole for
digital use ...

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[CDB-3]

:: Push-pull output has historically been used for valve and
:: transistor
:: amplifiers that have an output transformer with centre tapped
:: primary, each
:: half driven alternatively in a Class B configuration. This was the
:: configuration of output stage that every 6 transistor pocket radio
:: from the 50s through the 70s used.

One term I haven't seen used as an alternative to push pull in this
discussion is a complimentary pair output.

I also tend to think of P&P as that used by an amplifier with using an
audio transformer, and complimentary pair in push pull mode for thhe
transformerless version, so for ac signals.

I think one of my first electronics set of books by the venerable
G.N.Patchett referred to the valve amplifier radio circuit as push
pull and the transistor one as complimentary pair. Must race off and
buy some OC81's and 45's !

Colin
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[Gerhard Fiedler]

Alan B. Pearce wrote:

>> "Totem pole" and "push-pull" both mean the same thing.
>
> Not historically. I am with Olin on this one, but see below ...
>
> Push-pull output has historically been used for valve and transistor
> amplifiers that have an output transformer with centre tapped
> primary, each half driven alternatively in a Class B configuration.
> [...]
>
> Totem pole has historically been the term used for the likes of TTL
> logic output stages. [...]

So it seems you are saying that neither term is (in its "pure" meaning
:) to be used for a digital output that drives actively high and low
(with about equal drive capability). How would you call such outputs? Is
there a generic term for this capability?

FWIW, it seems that "historically" (for shorter values of "history" :)
I've seen "push-pull" being used a lot for digital outputs that drive
actively high and low (with about equal drive capability). May not be
the first meaning, but seems to be the more common meaning. AC
amplifiers with center-tapped transformers in the output are not that
common anymore.

BTW, I think there are a few terms that changed their meaning over time,
accompanying the changes in technology. I can't think of one right now,
but I'm sure some here can :)

Gerhard
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[Derward Myrick]

----- Original Message -----
From: "Alan B. Pearce" <Alan.B.Pearce@...>
To: "Microcontroller discussion list - Public." <piclist@...>
Sent: Monday, May 11, 2009 2:54 AM
Subject: Re: [EE] Push-pull vs totem pole

> >"Totem pole" and "push-pull" both mean the same thing.
>
> Not historically. I am with Olin on this one, but see below ...
>
> Push-pull output has historically been used for valve and transistor
> amplifiers that have an output transformer with centre tapped primary,
> each
> half driven alternatively in a Class B configuration. This was the
> configuration of output stage that every 6 transistor pocket radio from
> the
> 50s through the 70s used.
>
> Totem pole has historically been the term used for the likes of TTL logic
> output stages. These devices never used the term push-pull in their
> descriptions from the manufacturer.
>
> Possibly there has been some confusion arise through the use of push-pull
> for transformerless transistor output stages in audio amplifiers, which
> although of a totem pole style circuit configuration, used the term
> push-pull.
>
> So from this one ends up using push-pull for linear use, and totem pole
> for
> digital use ...
>
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Alan,

I am an old timer,electronics as hobby since late 1930s, and I agree with
you.  However I seem to remember in some TEK technical notes in the early
sixteys
seeing a tube circuit without a transformer that they called a totem pole.

Derward













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