Question on LT Spice equivalents...

Paul Burridge · Feb 8, 2004

On Sat, 07 Feb 2004 23:56:20 GMT, Roy McCammon
<rmccammon@austin.rr.com> wrote:

wow Chris

I have to admit that I haven't walked in your shoes. I might
feel the same way. If you are coping, then you are coping. A
person close to me also suffers from FMA; if she doesn't take
Prozac (vitamin P), its hard for us to cope with her.

There's no "one-size-fits-all" remedy for depression. It's a complex
disorder, poorly-understood and its origin in any given individual can
depend on many factors both endogenous and exogenous. Having said
that, Chris is in the minority as something like 73% of patients
respond well to chemical prophyaxis whatever the aetiology. That's
fortunate, because New Scientist magazine estimates that by 2050,
we'll *all* be depressed!

--

The BBC: Licensed at public expense to spread lies.

Jim Thompson · Feb 8, 2004

On Sun, 8 Feb 2004 01:52:51 +0000 (UTC), kensmith@violet.rahul.net
(Ken Smith) wrote:

In article <s09820lioekdbuf23d6rqkl902agcjh081@4ax.com>,
Jim Thompson <thegreatone@example.com> wrote:
[...]
Wrong. 'HC04 *is* buffered, it has three inverters in series.

Besides
over-driving the crystal

I disagree with this part of the statement. Both the buffered and
unbuffered devices limit at the point where the output swings from ground
to VCC. Assuming that the crystal is AT cut it is easy to design an
oscillator where the drive is not excessive.

The unbuffered will look sinusoidal on the input side and
quasi-sinusoidal on the output side.

it is prone to spurious oscillations

This is the real killer with buffered gates. They have so much gain that
all sorts of funny modes of oscillation can get started in them.

plus
significant slowing of the oscillation frequency.

This is only true at higher frequencies. At 1 or 2 MHz the effect is
small.

--

480)460-2350 | |
| E-mail Address at Website Fax

Jim Thompson · Feb 8, 2004

On Sun, 8 Feb 2004 02:27:38 +0000 (UTC), kensmith@violet.rahul.net
(Ken Smith) wrote:

In article <f36b20lkodjvcbek7aumuhkjtqt0a9fnf6@4ax.com>,
Jim Thompson <thegreatone@example.com> wrote:
On Sun, 8 Feb 2004 01:52:51 +0000 (UTC), kensmith@violet.rahul.net
(Ken Smith) wrote:

In article <s09820lioekdbuf23d6rqkl902agcjh081@4ax.com>,
Jim Thompson <thegreatone@example.com> wrote:
[...]
Wrong. 'HC04 *is* buffered, it has three inverters in series.

Besides
over-driving the crystal

I disagree with this part of the statement. Both the buffered and
unbuffered devices limit at the point where the output swings from ground
to VCC. Assuming that the crystal is AT cut it is easy to design an
oscillator where the drive is not excessive.

The unbuffered will look sinusoidal on the input side and
quasi-sinusoidal on the output side.

The buffered will look sinusoisal on the input side (unless you look real
closely) and quasi-sinusoidal on the output side (if you call a near
square wave quasi-sinusoidal). Since you know the amplitude, you can
design for the right drive level.

This is only true at higher frequencies. At 1 or 2 MHz the effect is
small.
74HC04: 8ns delay is 6.4% of the period of an 8MHz oscillator.

So at 1MHz it is less than 1%. I think you'd agree that this qualifies
for "the effect is small".
--

It's even *smaller* for the 'HCU04 and the gain is down dramatically.

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months... and the clients
kiss my feet... in a recent RF chip *only* my cells came out working
to specification ;-)

...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

Ken Smith · Feb 8, 2004

In article <s09820lioekdbuf23d6rqkl902agcjh081@4ax.com>,
Jim Thompson <thegreatone@example.com> wrote:
[...]

Wrong. 'HC04 *is* buffered, it has three inverters in series.

Besides
over-driving the crystal

I disagree with this part of the statement. Both the buffered and
unbuffered devices limit at the point where the output swings from ground
to VCC. Assuming that the crystal is AT cut it is easy to design an
oscillator where the drive is not excessive.

it is prone to spurious oscillations

This is the real killer with buffered gates. They have so much gain that
all sorts of funny modes of oscillation can get started in them.

plus
significant slowing of the oscillation frequency.

This is only true at higher frequencies. At 1 or 2 MHz the effect is
small.

--
--
kensmith@rahul.net forging knowledge

Ken Smith · Feb 8, 2004

In article <f36b20lkodjvcbek7aumuhkjtqt0a9fnf6@4ax.com>,
Jim Thompson <thegreatone@example.com> wrote:

On Sun, 8 Feb 2004 01:52:51 +0000 (UTC), kensmith@violet.rahul.net
(Ken Smith) wrote:

In article <s09820lioekdbuf23d6rqkl902agcjh081@4ax.com>,
Jim Thompson <thegreatone@example.com> wrote:
[...]
Wrong. 'HC04 *is* buffered, it has three inverters in series.

Besides
over-driving the crystal

I disagree with this part of the statement. Both the buffered and
unbuffered devices limit at the point where the output swings from ground
to VCC. Assuming that the crystal is AT cut it is easy to design an
oscillator where the drive is not excessive.

The unbuffered will look sinusoidal on the input side and
quasi-sinusoidal on the output side.

The buffered will look sinusoisal on the input side (unless you look real
closely) and quasi-sinusoidal on the output side (if you call a near
square wave quasi-sinusoidal). Since you know the amplitude, you can
design for the right drive level.

This is only true at higher frequencies. At 1 or 2 MHz the effect is
small.
74HC04: 8ns delay is 6.4% of the period of an 8MHz oscillator.

So at 1MHz it is less than 1%. I think you'd agree that this qualifies
for "the effect is small".
--
--
kensmith@rahul.net forging knowledge

Paul Burridge · Feb 8, 2004

On Sat, 07 Feb 2004 19:34:59 -0700, Jim Thompson
<thegreatone@example.com> wrote:

It's even *smaller* for the 'HCU04 and the gain is down dramatically.

So everyone's agreed the 74HCU04 is a perfectly suitable active
element to use in a crystal oscillator?
I've come across another hex inverter in my stash of parts. It's a
SC74AC04PC. I seem to recall the "AC" has some significance. Does
anyone know if this would be equally suitable for oscillatory
purposes? Or how about a Schmitt trigger? Too much gain, I suppose?

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months...

Curious. You'd be better off sticking with PSpice. Should cut the
development time down significantly. ;-)
--

The BBC: Licensed at public expense to spread lies.

Jim Thompson · Feb 8, 2004

On Sun, 08 Feb 2004 13:34:09 +0000, Paul Burridge
<pb@osiris1.notthisbit.co.uk> wrote:

On Sat, 07 Feb 2004 19:34:59 -0700, Jim Thompson
thegreatone@example.com> wrote:

It's even *smaller* for the 'HCU04 and the gain is down dramatically.

So everyone's agreed the 74HCU04 is a perfectly suitable active
element to use in a crystal oscillator?

Yes.

I've come across another hex inverter in my stash of parts. It's a
SC74AC04PC. I seem to recall the "AC" has some significance. Does
anyone know if this would be equally suitable for oscillatory
purposes?

No, it's buffered.

Or how about a Schmitt trigger? Too much gain, I suppose?

Schmitt triggers often don't start in XTAL oscillator applications.

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months...

That's just the chips with oscillators.

Curious. You'd be better off sticking with PSpice. Should cut the
development time down significantly. ;-)

480)460-2350 | |
| E-mail Address at Website Fax

Winfield Hill · Feb 8, 2004

Jim Thompson wrote...

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months... and the clients
kiss my feet... in a recent RF chip *only* my cells came out working
to specification ;-)

The question shouldn't be whether your oscillators work, but
whether they damage marginal crytals after extended use. :&gt

Thanks,
- Win

whill_at_picovolt-dot-com

Jim Thompson · Feb 8, 2004

On 8 Feb 2004 09:06:04 -0800, Winfield Hill
<Winfield_member@newsguy.com> wrote:

Jim Thompson wrote...

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months... and the clients
kiss my feet... in a recent RF chip *only* my cells came out working
to specification ;-)

The question shouldn't be whether your oscillators work, but
whether they damage marginal crytals after extended use. :&gt

Thanks,
- Win

whill_at_picovolt-dot-com

I have some GPS designs that have been working continuously for
probably 15 years without failure. (The *series* R sets the drive
level in inverter-style XTAL oscillators.)

I also have some NIC-based designs; and a number of serial-mode
designs; but they're *way* over the comprehension level of these
groups (require Algebra and thinking ;-)

...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

Jim Thompson · Feb 8, 2004

On Sun, 08 Feb 2004 13:53:07 -0800, Jamie
<jamie_5_not_valid_after_5_Please@charter.net> wrote:

Hmm, none of you guys work with Cat wiskers anymore?

[snip]

480)460-2350 | |
| E-mail Address at Website Fax

Paul Burridge · Feb 8, 2004

On 8 Feb 2004 09:06:04 -0800, Winfield Hill
<Winfield_member@newsguy.com> wrote:

Jim Thompson wrote...

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months... and the clients
kiss my feet... in a recent RF chip *only* my cells came out working
to specification ;-)

The question shouldn't be whether your oscillators work, but
whether they damage marginal crytals after extended use. :&gt

ROTFL! :-D
--

The BBC: Licensed at public expense to spread lies.

Paul Burridge · Feb 8, 2004

On Sun, 08 Feb 2004 11:46:38 -0700, Jim Thompson
<thegreatone@example.com> wrote:

On Sun, 08 Feb 2004 13:53:07 -0800, Jamie
jamie_5_not_valid_after_5_Please@charter.net> wrote:

Hmm, none of you guys work with Cat wiskers anymore?

[snip]

I did, when I was a kid. Also surface barrier transistors... just
about anything you can name.

It was you who invented the coherer, wasn't it, Jim? ;-)
--

The BBC: Licensed at public expense to spread lies.

Keith R. Williams · Feb 8, 2004

In article <102d0i4nom75bf5@corp.supernews.com>, jamie_5
_not_valid_after_5_Please@charter.net says...

Hmm, none of you guys work with Cat wiskers anymore?

Sure, when I want to tease the cat.

;-)

--
Keith

Klaus Vestergaard Kragelu · Feb 8, 2004

"Paul Burridge" <pb@osiris1.notthisbit.co.uk> wrote in message
news:l03d20p6eo09oc6q54o06a9ulfah2dddnc@4ax.com...

On 8 Feb 2004 09:06:04 -0800, Winfield Hill
Winfield_member@newsguy.com> wrote:

Jim Thompson wrote...

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months... and the clients
kiss my feet... in a recent RF chip *only* my cells came out working
to specification ;-)

The question shouldn't be whether your oscillators work, but
whether they damage marginal crytals after extended use. :&gt

ROTFL! :-D
--

Did you find that funny? You sure do have a special form of humor....

Cheers

Klaus

Jamie · Feb 8, 2004

Hmm, none of you guys work with Cat wiskers anymore?

Jim Thompson wrote:

On 8 Feb 2004 09:06:04 -0800, Winfield Hill
Winfield_member@newsguy.com> wrote:

Jim Thompson wrote...

Don't trifle with me, young man... I design a new microchip with a
XTAL oscillator at least once every three months... and the clients
kiss my feet... in a recent RF chip *only* my cells came out working
to specification ;-)

The question shouldn't be whether your oscillators work, but
whether they damage marginal crytals after extended use. :&gt

Thanks,
- Win

whill_at_picovolt-dot-com

I have some GPS designs that have been working continuously for
probably 15 years without failure. (The *series* R sets the drive
level in inverter-style XTAL oscillators.)

I also have some NIC-based designs; and a number of serial-mode
designs; but they're *way* over the comprehension level of these
groups (require Algebra and thinking ;-)

...Jim Thompson

James Meyer · Feb 9, 2004

On Sun, 08 Feb 2004 13:53:07 -0800, Jamie
<jamie_5_not_valid_after_5_Please@charter.net> posted this:

Hmm, none of you guys work with Cat wiskers anymore?

Once in a while I cough up a hairball.

Jim

James Meyer · Feb 9, 2004

On Sun, 08 Feb 2004 11:46:38 -0700, Jim Thompson <thegreatone@example.com>
posted this:

On Sun, 08 Feb 2004 13:53:07 -0800, Jamie
jamie_5_not_valid_after_5_Please@charter.net> wrote:

Hmm, none of you guys work with Cat wiskers anymore?

[snip]

I did, when I was a kid. Also surface barrier transistors... just
about anything you can name.

...Jim Thompson

Ever build a vacuum tube?

Jim

Jim Thompson · Feb 9, 2004

On Mon, 09 Feb 2004 03:54:58 GMT, James Meyer <jmeyer@nowhere.com>
wrote:

On Sun, 08 Feb 2004 11:46:38 -0700, Jim Thompson <thegreatone@example.com
posted this:

On Sun, 08 Feb 2004 13:53:07 -0800, Jamie
jamie_5_not_valid_after_5_Please@charter.net> wrote:

Hmm, none of you guys work with Cat wiskers anymore?

[snip]

I did, when I was a kid. Also surface barrier transistors... just
about anything you can name.

...Jim Thompson

Ever build a vacuum tube?

Jim

480)460-2350 | |
| E-mail Address at Website Fax

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