Driver to drive?

[Rich Grise]

On Wed, 24 Nov 2004 23:25:57 +0000, Ken Smith wrote:

Rich Grise <rich@example.net> wrote:

I guess that was too complex for you so I'll simplify it:

"Yes the temperature shows up in the equations"

other way. This is why technicians who slap together circuits by the seat
of their pants treat transistors as current-controlled, because it makes a
second-order expof***ingnentional term cancel the f**k out! Well, just
scale down by about two orders of magnitude. But really! Sheesh!

No they don't do that at all. They make this:

Vcc
!
--------+--------
! !
\ \
/ / R4
\R1 \
! !
! !/ c
+---------------!
! !\ e
! +-----
/ / !
\ R2 \ R3 ---
/ / ---
! ! !
! +-----
GND GND



R2 < 0.1 * R3 * (minimum HFE for this transistor)

Vb = Vcc * R2/(R1 + R2)

Ve - Vb - 0.7

This term seems to be a bone of contention. For one thing, what does
Ve - Vb - 0.7 evaluate to? And where is this value used?

If that's supposed to be "Ve = Vb - 0.7", it kinda blows away the
"voltage controlled" theory, since 0.7 is a constant.

Ie = Ve / R3

Gain = R4 * 25mV/Ie

And where does this 25 mV come from again?

Thanks!
Rich

 

[Jonathan Kirwan]

On Thu, 25 Nov 2004 02:30:42 GMT, Rich Grise <rich@example.net> wrote:

And where does this 25 mV come from again?

It comes from the term, kT/q, in the diode equation. (Ignoring the -1 term, the
derivative or slope.) It's more like 25.3mV at 25C and this voltage divided by
the emitter current gives you 're'.

The gain mentioned,

Gain = R4 * 25mV/Ie

if I read it correctly, isn't written right. I believe the assumption is that
the emitter capacitor is essentially a dead-short to whatever frequency is being
applied at the input and, because of this, the gain is roughly R4/re. Since re
is just the (25.3mV/Ie), then the gain would be: R4/(25.3mV/Ie) or
R4*Ie/25.3mV.

But I'll let the pros speak to this.

Jon

 

[Jonathan Kirwan]

On Thu, 25 Nov 2004 03:14:07 GMT, Jonathan Kirwan <jkirwan@easystreet.com>
wrote:

And where does this 25 mV come from again?

It comes from the term, kT/q, in the diode equation. (Ignoring the -1 term, the
derivative or slope.) It's more like 25.3mV at 25C and this voltage divided by
the emitter current gives you 're'.

I should add that re should also include the contact resistance (on the order of
around an Ohm.) At high Ie, it may dominate.

Jon

 

[Ken Smith]

In article <1fhaq0d1kpn55jcv02n1ns9bqtu7f2066c@4ax.com>,
Jonathan Kirwan <jkirwan@easystreet.com> wrote:

Gain = R4 * 25mV/Ie

if I read it correctly, isn't written right. I believe the assumption is that

Opps yes a typo.


Gain = R4 / 25mV/Ie

--
--
kensmith@rahul.net forging knowledge

 

[Rich Grise]

On Wed, 24 Nov 2004 19:09:38 -0800, Winfield Hill wrote:

Rich Grise wrote...

On Wed, 24 Nov 2004 23:25:57 +0000, Ken Smith wrote:
....
And where does this 25 mV come from again?

kT/q = 25.3mV at 68F = 20C. It's a justifiably-famous parameter that's
often call V_T. BTW, the 0.7 value is NOT a constant. See AoE page 80.
Using h_FE as a design parameter is not recommended, use Vbe instead.

Well, yeah, if you want to design it _right._ ;-) I was, after all, talking
about us ass-scratchers who just look at the book and throw a few parts on
the breadboard and if the meter deflects, go, "Good enough!" ;-)

Wait, that's not fair - the way I learned about transistors was by a
tutorial when I was quite young - pre-pubescent, I'm pretty sure, but you
know how us nerd geeks are about that whole puberty thing. Anyway, this
narrative that came with an educational kit was saying, "So, you've got
to apply a voltage to get current to flow. And you put a resistor in the
collector lead to drop the output voltage, and you've got to provide a
path for base current, so you add R2, but then you have to add R3 to
temperature compensate it so it doesn't blow itself up, and R4 to get the
gain and bias back into a sane ballpark, and of course, bypass R4 to get
some gain back at AC..." and so on. Strictly seat-of-the-pants, but it got
me through a 9-month USAF tech school in just over 3 months with a 95
average, (Radio Amateur's Handbook 1963 edition helped a lot too. )and
I've had a reputation for being able to fix stuff by just touching it, or
so it seemed. I could look at a schematic and just almost intuit what's
wrong with the unit, although a class on the detailed theory of operation
of each unit didn't do any harm in that regard.

But as a designer, I'm much better at simply copying the work of those who
have actually done the work. =:-O With their permission and full credit,
of course.

Thanks!
Rich

 

[Rich Grise]

On Thu, 25 Nov 2004 03:20:52 +0000, Ken Smith wrote:

In article <1fhaq0d1kpn55jcv02n1ns9bqtu7f2066c@4ax.com>,
Jonathan Kirwan <jkirwan@easystreet.com> wrote:

Gain = R4 * 25mV/Ie

if I read it correctly, isn't written right. I believe the assumption is that


Opps yes a typo.


Gain = R4 / 25mV/Ie

Or, how about G' = R4 / ((kT/q)/Ie) ?

Thanks,
Rich

 

[Siddhartha Jain]

Nicholas O. Lindan wrote:

Ah, yes. Goes by many names.

Hit the 'have you heard the news' button on the left and scroll down
1/3 for the newspaper add. Click on add to enlarge for reading.

http://www.merrillphoto.com/JunkStoreCameras.htm

This camera under the Canomatic name was sold for up to $299.00
and people bought it. When it was a Canomatic it was also a
"Video" camera.

But I imagine the Olympia's bargain $129 price is because it is
missing the "Multi-Angle Tripod".

At $12.95 you are being ripped off.

This thing is a landfill-liability. You need to be paid for
taking it.

Did I tell you it comes with a free bag? ;-)

Ohh well, sorry I didn't clarify in my original post that I DO NOT at
any time intend to use the camera for taking photographs - that what I
have a Canon 300D and Maxxum 5 for

I was solely looking at it for tearing it apart and re-using the
innards.

Maybe a link to some site where someone can describe in detail what
this camera actually consists of would help.

Thanks,

Siddhartha

 

[Active8]

On Thu, 25 Nov 2004 04:49:16 GMT, Rich Grise wrote:

<snip>

and
I've had a reputation for being able to fix stuff by just touching it, or
so it seemed.

I've seen a few VCRs with bad tracking probs. In each case, I looked
at the silk screen for the servo section and just run my finger over
the circuit. I figured I might see a change when I get to the
culprit. Each time the problem went away and I couldn't get it back.
--
Best Regards,
Mike

 

[Paul Burridge]

On Thu, 25 Nov 2004 03:14:07 GMT, Jonathan Kirwan
<jkirwan@easystreet.com> wrote:

On Thu, 25 Nov 2004 02:30:42 GMT, Rich Grise <rich@example.net> wrote:

And where does this 25 mV come from again?

It comes from the term, kT/q, in the diode equation. (Ignoring the -1 term, the
derivative or slope.) It's more like 25.3mV at 25C and this voltage divided by
the emitter current gives you 're'.

Also sometimes given as 1/40Ie(mA) in some text books, IIRC. Same
thing essentially.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Winfield Hill]

Ken Smith wrote...

Ge transistors often run away from collector junction leakage ...

That may be why GE hasn't made any transistors in a long time.


--
Thanks,
- Win

 

[Winfield Hill]

Rich Grise wrote...

somebody pulled a "provisional ballot" out of the air somewhere.

Just to make you happy, they weren't going to count it.

I voted Badnarik. He didn't win. )-;

They probably thought you were going to vote Kerry, a no-no.


--
Thanks,
- Win

 

[Kevin Aylward]

Winfield Hill wrote:

Ken Smith wrote...

Ge transistors often run away from collector junction leakage ...

That may be why GE hasn't made any transistors in a long time.

But you can always run after and catch them, one probably needs the
exercise.

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[N. Thornton]

"Siddhartha Jain" <losttoy2000@yahoo.co.uk> wrote in message news:<1101368895.735813.166520@z14g2000cwz.googlegroups.com>...

Ohh well, sorry I didn't clarify in my original post that I DO NOT at
any time intend to use the camera for taking photographs - that what I
have a Canon 300D and Maxxum 5 for

I was solely looking at it for tearing it apart and re-using the
innards.

Maybe a link to some site where someone can describe in detail what
this camera actually consists of would help.

why did you buy it if you dont know what to do with it?

NT

 

[Ken Smith]

In article <co4n4803tk@drn.newsguy.com>,
Winfield Hill <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Ken Smith wrote...

Ge transistors often run away from collector junction leakage ...

That may be why GE hasn't made any transistors in a long time.

Not "GE", "Ge", you know the stuff with 32 electrons. Germanium, not
geranium. Its harder to make transistors from geranium but easier to make
them from Germanium.

--
--
kensmith@rahul.net forging knowledge

 

[Siddhartha Jain]

N. Thornton wrote:

why did you buy it if you dont know what to do with it?

Haven't bought it yet. And thats what I asking - what all can be done
with it?

 

[Si Ballenger]

On 25 Nov 2004 09:23:31 -0800, bigcat@meeow.co.uk (N. Thornton)
wrote:

"Siddhartha Jain" <losttoy2000@yahoo.co.uk> wrote in message news:<1101368895.735813.166520@z14g2000cwz.googlegroups.com>...

Ohh well, sorry I didn't clarify in my original post that I DO NOT at
any time intend to use the camera for taking photographs - that what I
have a Canon 300D and Maxxum 5 for

I was solely looking at it for tearing it apart and re-using the
innards.

Maybe a link to some site where someone can describe in detail what
this camera actually consists of would help.


why did you buy it if you dont know what to do with it?

Where did he say he bought one?

 

[Rich Grise]

On Thu, 25 Nov 2004 09:58:34 -0800, Siddhartha Jain wrote:

N. Thornton wrote:

why did you buy it if you dont know what to do with it?


Haven't bought it yet. And thats what I asking - what all can be done
with it?

I think that's already been determined. You can take it apart, and you can
try to find uses for used parts from a cheap camera. Use the lens to
torture ants, use flash to make flashes, that sort of thing.

If you need to have ideas suggested to you as to what do with something
you want to buy just to trash it, then my suggestion is, save your money.

Buy something that will be useful, like a book.

Good Luck!
Rich

 

[Pig Bladder]

On Thu, 25 Nov 2004 15:01:14 +0000, Kevin Aylward wrote:

Winfield Hill wrote:
Ken Smith wrote...

Ge transistors often run away from collector junction leakage ...

That may be why GE hasn't made any transistors in a long time.

But you can always run after and catch them, one probably needs the
exercise.

No, no. That's Petticoat Junction!

--
The Pig Bladder From Uranus, still waiting for
some hot babe to ask what my favorite planet is.

 

[Pig Bladder]

On Thu, 25 Nov 2004 17:38:13 +0000, Ken Smith wrote:

In article <co4n4803tk@drn.newsguy.com>,
Winfield Hill <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:
Ken Smith wrote...

Ge transistors often run away from collector junction leakage ...

That may be why GE hasn't made any transistors in a long time.

Not "GE", "Ge", you know the stuff with 32 electrons. Germanium, not
geranium. Its harder to make transistors from geranium but easier to make
them from Germanium.

Geraniums?. Those are the flowers that were discovered in Gerany, right?

--
The Pig Bladder From Uranus, still waiting for
some hot babe to ask what my favorite planet is.

 

[Peter Chant]

On Wed, 24 Nov 2004 15:09:23 -0800, Bob Harrington wrote:

Golly - this is as good as that plastic TV satellite dish antenna that
was "Totally legal to own because it *Doesn't Tune Actual Satellite
Signals!*" =}

Ah, its not just me those ads annoy.

Pete