Driver to drive?

[Winfield Hill]

Ken Smith wrote...

In article <cn81ug02too@drn.newsguy.com>,
Winfield Hill <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:
Ken Smith wrote...

[...]
For the OP I'm adding a bit of extra working things out.

I've added a capacitor to the drawing called "Cbig" and labled some
resistors.

The TIP35 and TIP36 transistors are fairly cheap. I think I'd start
like this:

10 each TIP35
------------------- ---/\/\---
! \ /e R4 !
! ----- !
! TIP36 ! !
+-/\/\/-- -----------/\/\------+
! R2 e \ / R3 !
! ------ !
! ! --------- !
---+--/\/\/\/--+-----! LM317 !---------+-+--
R1 --------- !
! --- Cbig
---
!
GND

The TIP35 and TIP36 are slow. They are extra slow when their collector
voltage drops below about 2V. Along with the usual bypass an LM317 needs,
you also need some added largish capacitor to make up for the fact that it
will take the TIP35,36 stuff time to throttle up and down. The
minimum value of this capacitor I would extimate like this:

Assume that the 150A draw starts suddenly.
Assume that the voltage can droop or spike up by 0.1V.

The TIP35 and 26 have a rise and fall time of about 0.25uS (Check data
sheet to be sure)

The TIP36 has to turn on and then the TIP35 so the total time is 0.5uS.

Rather than having to integrate, we just say the TIP35 and TIP36 stuff
doesn't do anything for 0.5uS and get an over estimate of the minimum.

In 0.5uS, 150A will transfer a charge of 75uC.

The voltage change on the Cbig will be:

V = Q / C

where
Q is the charge
C is the capacitance

We solve for C


C = Q / V = 75uC / 0.1 = 750uF

Now here's the messy bit. We have assumed tha Cbig has no resistance.
All real parts have some resistance. We now need to find the data sheet
on some lets say, 1000uF capacitor with a nice low Equivelent Series
Resistance (ESR) to see how much drop will appear in the ESR. If that
plus the droop in the 1000uF is more than the specification, you need a
larger capacitor.


Finding R1:

If the circuit is lightly loaded, we want the LM317 to pass all of the
current. This means that there should be less than about 0.6V on R1 when
a "small current" is drawn. We will define a small current as 50mA os we
can say

R1 = 0.6V / 0.05A = 12 Ohms

So we make R1 about 12 Ohms.


About R2:

R2 could in most cases be zero. It lowers the gain of the TIP36 part of
things and works to reduce the risk of oscillation. I'd make this a low
inductance resistor of about 0.01 Ohms or a short length of wire.


About R3:

We want about an Amp flowing in the TIP36 before the TIP35s are brought
into things. R3 is something like 0.1 to 1.0 Ohms.


About R4:

This is actually 10 resistors, one resistor in the emitter leg of each
TIP35. When a bipolar transistor heats up, its Vbe drop decreases. If R4
wasn't there, the hottest TIP35 would end up taking on more than its share
of the load, get hotter, draw more, get hotter and etc. This could
destroy one transistor.

Thermal resistance is a lot like electrical resistance. Heat sources are
like current sources. All of the heat must flow out of one transistor
through all of the stuff it goes through to get out to the environment.
In process, one transistor will tend to warm up its brothers. To find the
minimum R4 we start with assuming a current flows in one transistor and
work out how much its temperature rises above the coolest of its brothers.
To make the math easy, just assume 1A flows.

One you have the temperature rise, assume that the individual R4 must add
at least 2.5mV of drop for every amp flowing. It is likely that this will
be such a small value that using 10 wires running from the TIP35s to the
load instead of one big oun will be enough to do it.



A note about layout:

You want Cbig to be as close to the load as practial. Ideally, there
should be 12 wires to the (+) side of the load. The LM317, the TIP36 and
all the TIP35s each have a wire. These wires should be tightly bundled
together.


A note about fuses:

They make special fuses for things like car starter motors. They look
like a thick cable with a wide section in it. Put one of these between
the car battery and the circuit. A car battery can produce nearly
infinite current for a short time.

Winfield Hill wrote...

. 7.2V 150A Linear Regulator
. BATT 250A fuse by Winfield Hill
. POS __or breaker
. =====|__|==(O)===+===+===+===+===+===+===+===+===+===+===+===+===+===+===+
. +12.5-14.5V | | | | | | | | | | | | | | |

Yes that's a good point. I learned about this by examining my 1985 Cougar
with the help of Chilton and Haynes manuals. The engine compartment is
filled with 20, 30, 40 and 60A distribution fuses for various things, plus
single 175A "Mega fuse" to the generator and "distribution block" (called
a fuseable link on some models). Mine is a removable plastic-encased fuse.

There is also a 15A and an 80A fuse bypassing the Mega fuse. In the case
of these Ford models the starter motor is _not_ fused. With some effort
these big replaceable fuses can be procured as automotive spare parts.


--
Thanks,
- Win

 

[Guy Macon]

Tim Wescott wrote:

The OP would have to clarify, but it appears he wants each external
pulse to be given a value of 5 seconds and counted -- if so then no
real-time clock is necessary.

This would certainly be something that affects processor choice!

Ah. My error. Alas, I am out of town and away from my lab, and am
trying to make intellegent comments based on what I can find through
a web search.

 

[CBarn24050]

Subject: Microcontroller help needed
From: "Kim" ksleep@sympatico.ca
Date: 14/11/2004 05:24 GMT Standard Time
Message-id: <i1Cld.53162$Z7.1588245@news20.bellglobal.com

I don't have enough experience, or common sense to complete this project, so
I need some help, and finally realised that I will have to pay for someone
else to do it for me

These kind of jobs are expensive to have done. With some effort you should be
able to do it yourself and there are lots of helpful people who can get you
back on track each time you get lost. To answer your question: I have a module
4" x3" x 1/2" plus display, batteries and programmed $400.

 

[Rich The Philosophizer]

On Sun, 14 Nov 2004 10:15:13 -0800, Tim Wescott wrote:

Oddly enough I almost never do that in practice -- its only when I have
an audience that I screw up in such a stupid way.

Don't worry, Tim. _I_ saw the one that got away. ;-)

 

[Rich The Philosophizer]

On Sun, 14 Nov 2004 17:33:16 -0600, John Fields wrote:

On Sun, 14 Nov 2004 23:17:37 GMT, Rich The Philosophizer
null@example.net> wrote:

On Sun, 14 Nov 2004 10:05:53 -0600, John Fields wrote:

On Sun, 14 Nov 2004 09:22:17 GMT, Rich The Philosophizer
null@example.net> wrote:

Well, the most recent "information" I've heard about Fallujah was that
there was surprisingly little resistance encountered, and they're about
to declare it "secure."

What would it happen if the "terrorists" just laid low for a few
months, acting like it's normal friendly occupation forces, serving
drinks in the off-base clubs and all that "entertain the GIs" crap,
and when it's loaded with GIs, and it's so secure that troops are
going there for R&R from Afghanistan and Pakistan, and when it gets
loaded to capacity, blow up the whole town?

---
Then the whole town and everybody in it would be killed.

Yes, we established that in the previous paragraph.

---
Hmmm... maybe it's just me, but when someone starts a paragraph with a
question, like: "What would happen if"... and then doesn't answer it,
I kinda tend to think that it needs to be answered before anything's
really "established".
---

Then what?

---
Hey, it's _your_ movie, so what would _you_ do?

You know I never would have invaded in the first place, so that's
a non-answer.

I'm talking about speculating about scenarioos, but evidently I've
jumped-thread or something.

Thanks anyway,
Rich

 

[sjcma]

Rich Grise wrote:

On Sat, 13 Nov 2004 21:23:13 -0500, sjcma wrote:


As far as I know, there isn't. The way I learned it, the definition
of a Colpitts is a parallel resonant circuit with a tapped capacitor,
with signal ground at the junction of the caps, so the ends are 180
degrees out of phase, so it's a natural feedback path. Or something
like that. One end to the output and the other to the input, basically.
And the Hartley is the same thing with the coil and caps swapped. ;-)

The rest is window dressing.

Hi Rich,

I've seen circuits like that described as being a Colpitts oscillator.
But I've also seen the exact same circuit being described as a Pierce
oscillator, where an inverting amplifier (could be a digital inverter)
is attached to a parallel-C, series L or crystal, and parallel-C before
feeding back to the input of the inverting amplifier.

So is it a Colpitts or Pierce? Or is the Pierce name strictly for xtal
oscillators?

Stan

 

[sjcma]

Kevin Aylward wrote:

Well, I disagree with the other definitions in this thread on the taped
cap, especially the one by Tim with no cap directly from collector to
emitter. Here's the real deal.

Consider 3 impedances on a transister. Zcb, Zbe Zce.

The load on the collecter is Zce || (Zcb + Zbe).

The loop gain is therefore:

Av = gm.(Zce || (Zcb + Zbe)).Zbe/(Zbe + Zcb)

Setting this to one, one finds that the only too solutions are where
Zbe, Zce are capacitice with Zcb inductive or Zbe, Zce are inductive
with Zcb capacitive.

That is, a Colpits oscillator is when, topological, there are caps
across base emitter and collector emitter, with an inductance from base
to collector (Colpits), or where the caps and inducters are swaped
(Hartly).

Kevin Aylward

Hi Kevin,

Thanks for a brilliantly clear explanation.

So how should one go about choosing which of the three terminals of the
transistor to ground? What are the pluses and minuses of each of the
three options?

Stan

 

[Active8]

On Sun, 14 Nov 2004 10:15:13 -0800, Tim Wescott wrote:

Kevin Aylward wrote:


That is, a Colpits oscillator is when, topological, there are caps
across base emitter and collector emitter, with an inductance from base
to collector (Colpits), or where the caps and inducters are swaped
(Hartly).

Argh. Yes, I got the transistor in there wrong -- I was concentrating
on the nifty notion that you draw the circuit free of any entanglements
from bias networks, then you ground whatever point is most convenient
for you.

Oddly enough I almost never do that in practice -- its only when I have
an audience that I screw up in such a stupid way.

@#$%! See Kevin Aylward's comments -- I got my transistor in there
wrong. All other comments apply.

.------o------.
| | |
| --- |
| --- |
C| | ---
C| o-----v \--.
C| | |
| --- |
| --- |
| | |
'------o----------'

What about - I've seen this, but it's an n-fet, not an npn. The c-e
cap isn't part of the tank, per se, but it's a bypass - ?

+---------+
| |
| Bypass |
|/ ---
+----------+------| ---
| | |> |
| --- | |
| --- | |
C| | | |
C| +--------+---- out |
C| | |
| --- |
| --- |
| | |
+----------+------------------+-- GND, IIRC

created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

--
Best Regards,
Mike

 

[Active8]

On Mon, 15 Nov 2004 01:03:51 -0500, sjcma wrote:

So how should one go about choosing which of the three terminals of the
transistor to ground? What are the pluses and minuses of each of the
three options?

My guesses:

CE - big swing moderate output Z.

CC - low Z out for driving a buffer. Osc isn't loaded or Miller
f*cked by the load.

CB - keeps the swing from exacerbating the Miller / Early effects.

'twas a good qweshtion
--
Best Regards,
Mike

 

[Bill Sloman]

John Fields <jfields@austininstruments.com> wrote in message news:<hcnep052toe7iu78dqhg191jg5f930jtfu@4ax.com>...

On 13 Nov 2004 15:28:15 -0800, bill.sloman@ieee.org (Bill Sloman)
wrote:

John Fields <jfields@austininstruments.com> wrote in message news:<imacp09ug5gr716a2l4mcgnmdes5uu41jd@4ax.com>...

---
OK, but disenfranchisement because of ignorance isn't going to happen
(again) anytime soon, I think.
---

Self-serving optimism.

---
Sure. I see the glass half full and filling, while you see the glass
half empty and emptying. Besides, I can't think of any optimism which
_isn't_ self-serving, can you?
---

I seem to be able to think of lot of things that you don't - you do
have the disadvantage of living in Texas, where they don't start
teaching you about the world outside Texas until you get to secondary
school, and it does show.

There are Texans who are sophisticated enough to know that they don't
know much about the outside world, but you don't seem to be one of
them.

Sounds to me like a case of the literati being more equal than the
illiterati.

As it should be. Do you want your diseases treated by someone who
lacks a medical education?


---
Apples and oranges.

Scarcely. Medical practitioners treat diseases of the body,
politicians treat diseases of society. We've got legal rules that
prevent medical quacks from offering their services to the sick, and -
with Dubbya as a prime example - we need similar rules to prevent
political quacks from offering their services to the country.

Since politicians make the rules, we can't simply license politicians,
as we do doctors, because the politicians in power would then just
license only their friends and allies, so we have to work on the
electoral process to stop the quacks getting elected in the first
place.

This means organising the electoral process so that the actual voting
population is dominated by voters with the capacity to detect quacks.
There are lots of ways of doing this. Banning party political ads on
television strikes me as one of the more promising.

---

What do you suggest? A purge? Sterilization?
Euthanization of the offspring of parents with IQ's lower than _or_
higher than "x"? Euthanization of that portion of the population with
equally "unacceptable" IQ's?

Electoral expenditure rules with teeth, so that multi-millionaires
can't buy up TV time to push electoral misinformation into the brains
of the couch potatoes.

---
Agreed, but I'd go farther than that.
As part of the licensing procedure for commercial broadcast stations
I'd include a requirement for the donation of a certain amount of free
time during election years (perhaps restricted to a month or so before
the election) for each/all of the candidates who have managed to meet
certain requirements; perhaps 100,000 signatures. Dunno... haven't
worked it out yet. What do you think?

I think that that is a terrible idea, even though that is pretty much
exactly what they do in the U.K. at the moment, because it makes it
even more dificult to set up new political parties.

The one benefit of the UK system of party political broadcasts is that
the TV time is dealt out as a limited number of roughly ten minute
slots, and the broadscasts are so excruciatingly boring that even the
most torpid of couch potatoes goes to the trouble of changing the
station to get away from them.

It is the 90 second political advertisement that is the real problem -
it is aimed at the non-critical viewer, and is long enough to contain
a simple message, and short enough to fit into the attention span of
the dumbest voter.

Make them longer, and the vacuity of the message becomes obvious to
the smarter viewers, while the dumber viewers tune out, which is why
TV advertisers go for 90 second spots.

-------
Bill Sloman, Nijmegen

 

[Rich The Philosophizer]

On Thu, 11 Nov 2004 17:11:05 +0000, Rolavine wrote:

From: Rich The Philosophizer null@example.net


On Wed, 10 Nov 2004 20:40:23 +0000, Dirk Bruere at Neopax wrote:

Product developer wrote:

John Fields <jfields@austininstruments.com> wrote in message

On Wed, 10 Nov 2004 15:24:57 GMT, Fred Bloggs <nospam@nospam.com
wrote:


Squeezing jello in Iraq
By Scott Ritter

---
Scott Ritter is a traitorous son of a bitch who should be shot.


Only a degenerate like Bloggs could rely on the words of another
degenerate.

Scott Ritter - Traitor - Was Arrested Soliciting Sex from Teenage Girl
By: Capital News 9 web staff
According to newspaper reports this weekend, former UN weapons
inspector and Delmar native Scott Ritter was arrested for a Class B
misdemeanor.

Only in the nation that freaked when it saw Janet Jacksons tit does this
matter.

Yeah - and this in the country where two out of three commercials are for
hardon pills.

Thanks,
Rich

I think it's time to give rich the Prestigious SElecDesign WAG Award!

Do I hear a second!

Oh, please, no awards. I've got awards coming out my ass. And if you've

ever had awards coming out your ass, you know how painful that can be.
<rimshot>

Just send money. Or better yet, exotic masseuses. Exotic, bisexual,
female masseuses. <leer, snort>

;^j
Rich

 

[Dirk Bruere at Neopax]

Rich The Philosophizer wrote:

On Wed, 10 Nov 2004 21:46:17 +0000, Dirk Bruere at Neopax wrote:


Terry Given wrote:


Dirk Bruere at Neopax wrote:


Paul Burridge wrote:


On Wed, 10 Nov 2004 04:49:20 GMT, Rich The Philosophizer
null@example.net> wrote:



On Tue, 09 Nov 2004 20:42:03 +0100, Frithiof Andreas Jensen wrote:



"Fred Bloggs" <nospam@nospam.com> skrev i en meddelelse
news:418D5DA1.1010609@nospam.com...


Apparently this is still practiced:

"However, a small number of Orthodox rabbis advocate an ancient
practice in which the circumciser sucks



And I thought the Catholic Church had problems ;-))



Nah, they only drink the blood and eat the flesh of some dead guy, who
also happens to be their main icon.

God Forbid they should ever accidentally get their mouth near the
mutilated penis of a helpless baby!




They're not *still* engaging in this odious 'practice' are they? I
thought we'd agreed to ban it. Why hasn't our edict outlawing this
Satanic abuse been observed?



Makes the term 'cocksucking Jew' quite accurate in some cases eh?
Stands right besides 'Xian bugger'.


ROTFLMAO!

The Catholic church might be a better place if one of the commandments
had read "Thou shalt not rape little boys"

Well, Islam seems to have got it partially correct.
They can officially screw 10yr old girls.


Now, wait a minute. I can't believe that there's _any_ religion
that allows sex with underage children. There must have been something
missing in the translation.

Could you shed some light on this matter? Or is it just another
boogeyman thing?

Thanks,
Rich


http://www.islamreview.com/articles/sexinislam.shtml

The Prophet of Islam, Muhammad (pbuh), himself married a child of six (or seven)
years old. Many articles have recently been written about this child bride of
Muhammad. I shall refer the readers to read those articles elsewhere. Here are
two hadith from the Sahi (authentic) of all ahadith to confirm the marriage of
Muhammad (pbuh) with a child who was still playing with her dolls when the
Prophet of Islam took her to his house to consummate (to have sex with her) the
marriage.
Sahih Muslim Book 008, Number 3311:

'A'isha (Allah be pleased with her) reported that Allah's Apostle (may peace be
upon him) married her when she was seven years old, and he was taken to his
house as a bride when she was nine, and her dolls were with her; and when he
(the Holy Prophet) died she was eighteen years old.

Sahih Bukhari Volume 5, Book 58, Number 236:

Narrated Hisham's father:
Khadija died three years before the Prophet departed to Medina. He stayed there
for two years or so and then he married 'Aisha when she was a girl of six years
of age, and he consumed that marriage when she was nine years old.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Rene Tschaggelar]

George Gabriel wrote:

Hello to everybody,
as a part of my thesis work I'm trying to design a device for driving
piezoelectric transducers, to be used as a portable non-destructive
testing device.

I have lots of troubles in finding some good technical documentation
about probes. I'm quite confused so I think it's a good idea to ask for
help, before I'll go brain-dead.

Piezos are never driven with 50 Ohms, rather with a a bipolar
emiterfollower or Opamp, and some series resistor. The series
resistor serves multiple purposes :
- limit charging current and power dissipation in PZT
- limit bandwidth
- provide a drivable load to the OpAmp, as they don't like caps.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

 

[Bill Sloman]

John Fields <jfields@austininstruments.com> wrote in message news:<rqjep0h0nmldc5h5c8j33eo0vs25neiuqp@4ax.com>...

On 13 Nov 2004 15:21:09 -0800, bill.sloman@ieee.org (Bill Sloman)
wrote:

<snip>

I'm not going anywhere,

We've noticed.

------
Bill Sloman, Nijmegen

 

[Dirk Bruere at Neopax]

John Fields wrote:

On Mon, 15 Nov 2004 13:08:26 +0000, Dirk Bruere at Neopax
dirk@neopax.com> wrote:


JeffM wrote:


::o you know the difference between a battle and a war?
::irk Bruere
:::

I do.
http://64.233.179.104/search?q=cache:LZRfLYD-gR8J:www.usconstitution.net/xconst_A1Sec8.html+The-Congress-shall-have-Power+To-declare-war

Yes. I also know that one can win all the battles and still lose the war.
The US is an expert in this.


---
Only lately, and only because we've let others talk us out of the win.
We really do need to stop listening to wimps.

ie your own electorate.
Don't worry - Bush is going to fix that 'democracy' problem you have.

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Chuck Olson]

"Chuck Olson" <chuckolson01@REMOVETHIScomcast.net> wrote in message
news:6fOjd.72872$R05.33169@attbi_s53...

After playing with a large clock by La Crosse Technology and seeing how it
is built, I ran across some clocks by SkyScan at the flea market (also
available from Fry's Electronics). What a difference! The PCBs in these
clocks are very nice epoxy-glass boards, with gold-plated "vias", which
make
wonderful test points. I bought one large wall clock, two medium size
table
clocks and one small travel alarm, for a total expenditure of around $17.
I
believe these are "return to vendor" items, but all four operated
flawlessly, and displayed greater sensitivity than the La Crosse units.
Maybe the manufacturer repaired them. In any event, examining the little
travel alarm, I was able to figure out which is the receiver output node
by
finding the 100K pull-up resistor (the only resistor on the receiver
board)
and monitoring the signal with a scope probe - - there must have been some
WWVB signal coming through in the afternoon after I pressed the "Receive"
button, because I could see intermittent down-going pulses from the 1.5
volt
Vcc level occurring over a period of time. I will build a simple FET
diff-amp with an LED in the output drain to monitor the state of this line
as I move the clock around. I'll report on results.

Chuck

The diff-amp idea wasn't the best way to go, due to the limited voltage
available, and the need to keep source circuit loading to a minimum.
Instead, I used a VN10K mosfet and a Bell Audiolarm beeper to provide an
audible indication of the signal quality. The results with the Travel Alarm
that used a single AAA cell were disappointing, with broken-up mark states
all during the time-code sequence, even with fairly strong signals as
measured with my FET source-follower loopstick feeding my IC-765. I
abandoned the Travel Alarm and went to the medium-size clock with the
electroluminescent back light, all operating on two AA cells, and that drove
the VN10K and beeper just fine, with solid code sequence reception even in
the daytime, and at nighttime even with the ferrite antenna oriented
north-south rather than the maximum-signal east-west position. I'd be glad
to answer any questions regarding where to connect the readout beeper or
other areas of interest, if I can.

Chuck W6PKP

 

[Ban]

Rene Tschaggelar wrote:

George Gabriel wrote:

Hello to everybody,
as a part of my thesis work I'm trying to design a device for driving
piezoelectric transducers, to be used as a portable non-destructive
testing device.

I have lots of troubles in finding some good technical documentation
about probes. I'm quite confused so I think it's a good idea to ask
for help, before I'll go brain-dead.

Piezos are never driven with 50 Ohms, rather with a a bipolar
emiterfollower or Opamp, and some series resistor. The series
resistor serves multiple purposes :
- limit charging current and power dissipation in PZT
- limit bandwidth
- provide a drivable load to the OpAmp, as they don't like caps.

Rene

The US probes he is refering to need a pulse of 100 to 400V to produce a
noticable output, this is done by discharging a capacitor of suitable size
into the probe. The probes work in different frequency ranges from 1MHz to
100MHz, depending on the desired resolution and depth. The faster(smaller)
ones you can operate with an avalance transistor, which gives the best rise
times.
The receiver is in parallel with the transmitter and is protected by a diode
ring made with si-carbide diodes or Schottky diodes for the lower voltages.
www.Krautkramer.com is the leading manufacturer of ultrasonic flaw
detectors. I have been designing for them .
--
ciao Ban
Bordighera, Italy

 

[John Fields]

On Mon, 15 Nov 2004 17:47:48 +0100, Rene Tschaggelar <none@none.net>
wrote:

Piezos are never driven with 50 Ohms, rather with a a bipolar
emiterfollower or Opamp, and some series resistor.

---
Not necessarily true.

I've designed multi-kilowatt underwater projectors driven by a 50 ohm
source by doing what was necessary to get a conjugate match to the
ceramic.

Wanna see some pictures of them in action?

--
John Fields

 

[John Fields]

On 15 Nov 2004 09:05:11 -0800, bill.sloman@ieee.org (Bill Sloman)
wrote:

John Fields <jfields@austininstruments.com> wrote in message news:<rqjep0h0nmldc5h5c8j33eo0vs25neiuqp@4ax.com>...
On 13 Nov 2004 15:21:09 -0800, bill.sloman@ieee.org (Bill Sloman)
wrote:

snip

I'm not going anywhere,

We've noticed.

---
You get to see what you're allowed to.

--
John Fields

 

[Don Pearce]

On Mon, 15 Nov 2004 12:50:12 -0600, John Fields
<jfields@austininstruments.com> wrote:

On Mon, 15 Nov 2004 17:47:48 +0100, Rene Tschaggelar <none@none.net
wrote:

Piezos are never driven with 50 Ohms, rather with a a bipolar
emiterfollower or Opamp, and some series resistor.

---
Not necessarily true.

I've designed multi-kilowatt underwater projectors driven by a 50 ohm
source by doing what was necessary to get a conjugate match to the
ceramic.

Wanna see some pictures of them in action?

If you were conjugate matching, you weren't driving them from 50 ohms.

d
Pearce Consulting
http://www.pearce.uk.com