common emitter configuration- voltage divider biasing.

[Joe]

"Robert C Monsen" <rcsurname@comcast.net> wrote in message
news:NOXOc.204882$JR4.201568@attbi_s54...

"Joe" <nuisancewildlife@nospamearthlink.net> wrote in message
news:z6TOc.21434$iK.18860@newsread2.news.atl.earthlink.net...

Hi Jon,

Ok, so, judging from the other responses, I have been looking at
things sort
of bass ackwards


Just to throw in my 2 cents, as I understand it, the emitter resistor
bypass cap is there to increase the gain as the frequency increases.
The gain of the amp is equal to the collector resistor divided by the
effective emitter resistance. If you put in a cap parallel to the
emitter resistance, what happens is that at higher frequencies, that
effective emitter resistance decreases (the cap 'shunts' or shorts the
higher frequency currents to ground.) Thus, doing this increases the
gain of the simple common emitter amp.

Somebody asked why you might want to do this. I think the answer is
that these days, if controlled gain is required, its generally
accomplished by using negative feedback. Negative feedback is more
effective if the open loop gain is higher, so getting the highest gain
you can is a good thing, even if you aren't able to control it very
effectively.

All of this is described quite well in "The Art of Electronics", 2nd
edition, chapter 2. If you really want to understand how all this
stuff works, or at least get a basic understanding of how to work the
formulas and bias an amp, go check out that book from the library and
read chapters 1 and 2. The feedback discussions are in chapter 4, I
think, and are also well worth the work.

Regards,
Bob Monsen

Thanks Robert,

I have seen that book in the local bookstore. I can probly read the
appropriate chapters right there, since my local library does not carry much
in the way of electronics books.

Joe

 

[Jonathan Kirwan]

On Sun, 01 Aug 2004 19:15:33 GMT, "Joe" <nuisancewildlife@nospamearthlink.net>
wrote:

My default font says it is 'courier new' whatever that means.

Okay, that's probably right, then. So, you still cannot read the ASCII
schematics? Frankly, I'm worried that what you are reading as "default font"
isn't what is being used to display the text. But I suppose you know what you
are doing.

If you are willing to go to some lengths, just to check it, highlight and copy
the text you are reading and then paste it into NOTEPAD. Save as text file.
Drop into DOS box, type it onto the screen. That'll make sure. (Or, you could
simply make sure that NOTEPAD is using a non-truetype system font or else
Courier New.)

The reason I say all this is that *I* have a great deal of difficulty with them
when the font is a proportional spaced font -- often, they are simply illegible.
Sometimes, just 'poorly formed' but 'readable, with some pain.' But if the font
is fixed-spacing, it should look readable. Of course, I'm assuming you know
that -/\/- is a resistor and --||-- is a capacitor, etc.

Jon

 

[Joe]

"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in message
news:tiiqg0ppmuu3ig216k0jjsssd9e70h5lpg@4ax.com...

On Sun, 01 Aug 2004 19:15:33 GMT, "Joe"
nuisancewildlife@nospamearthlink.net
wrote:

My default font says it is 'courier new' whatever that means.

Okay, that's probably right, then. So, you still cannot read the ASCII
schematics? Frankly, I'm worried that what you are reading as "default
font"
isn't what is being used to display the text. But I suppose you know what
you
are doing.

If you are willing to go to some lengths, just to check it, highlight and
copy
the text you are reading and then paste it into NOTEPAD. Save as text
file.
Drop into DOS box, type it onto the screen. That'll make sure. (Or, you
could
simply make sure that NOTEPAD is using a non-truetype system font or else
Courier New.)

The reason I say all this is that *I* have a great deal of difficulty with
them
when the font is a proportional spaced font -- often, they are simply
illegible.
Sometimes, just 'poorly formed' but 'readable, with some pain.' But if
the font
is fixed-spacing, it should look readable. Of course, I'm assuming you
know
that -/\/- is a resistor and --||-- is a capacitor, etc.

Jon

Thanks Jon,

No I am not familiar with what the symbols are in an ascii schematic. I
guess that's part of the problem. I'll google on ascii schematic and see if
I can find out.

Joe