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From: Jon Kirwan on 21 Dec 2009 15:35
On Sun, 20 Dec 2009 23:53:55 -0600, "Dave" <db5151(a)hotmail.com> wrote:

>How can one tell if one has the optimum setup for biasing a bipolar
>transistor, while it's still all on paper? There must be a way, I just
>don't know what it is, and am thinking that it's not necessary to build the
>damn thing every time to *see* if it works.

Single BJT common emitter voltage amp? If so, I can walk you through
some of the details.

Jon
From: Charles on 21 Dec 2009 17:08

http://www.ee.cityu.edu.hk/~hkng/doc07_08/L07%20DC%20and%20AC%20Load%20Line.ppt#7

Please check this out ... I think it fits your needs.


From: John Larkin on 21 Dec 2009 23:11
On Sun, 20 Dec 2009 23:53:55 -0600, "Dave" <db5151(a)hotmail.com> wrote:

>How can one tell if one has the optimum setup for biasing a bipolar
>transistor, while it's still all on paper? There must be a way, I just
>don't know what it is, and am thinking that it's not necessary to build the
>damn thing every time to *see* if it works.
>
>Many thanks,
>
>Dave
>

Building it is the worst way to design the bias bits, unless you
intend to only ever build one. Transistor betas can vary over a 10:1
range, and Vbe changes about 2.5 millivolts per degree C, and
transistors often self-heat. A bias design should be reasonably
insensitive to those effects.

If you can't do it analytically, simulate it with LT Spice. But vary
beta and Vbe to make sure it will work over the full datasheet beta
range and over temperature.

John

From: Edmond H. Wollmann on 22 Dec 2009 04:17

"Andrew Holme" <ah(a)nospam.co.uk> wrote in message news:umJXm.102934$2u1.52673(a)newsfe16.ams2...
>
> "Dave" <db5151(a)hotmail.com> wrote in message
> news:x9-dnXPZ3NzrkLLWnZ2dnUVZ_jKdnZ2d(a)posted.internetamerica...
>> How can one tell if one has the optimum setup for biasing a bipolar
>> transistor, while it's still all on paper? There must be a way, I just
>> don't know what it is, and am thinking that it's not necessary to build
>> the damn thing every time to *see* if it works.
>>
>> Many thanks,
>>
>> Dave
>>
>>
>
> Simulation?
>
> Why not use LTSpice? It's fantastic and free.
>
> I'm playing with it right now, studying an old design for a discrete
> transistor DC amplifier.
>


It will rust your brain.


From: Edmond H. Wollmann on 22 Dec 2009 04:19

"pimpom" <pimpom(a)invalid.invalid> wrote in message news:hgnm1o$n6l$1(a)news.albasani.net...
> Dave wrote:
>> How can one tell if one has the optimum setup for biasing a bipolar
>> transistor, while it's still all on paper? There must be a way, I
>> just don't know what it is, and am thinking that it's not necessary
>> to build the damn thing every time to *see* if it works.
>>
>
> The question must first be asked: optimum in what respect? There are several
> factors that may influence the choice of biasing circuit. E.g., -
> - stability with variations in temperature
> - stability with variations in power supply
> - stability with variations in transistor characteristics from sample to
> sample
> - for linear amplification, expected amplitude of input and output swing
> and there are others like noise, frequency response, impedance, gain, power
> dissipation, waveform distortion, dc and ac feedback, etc.
>


Yup, and also it's depending on what circuit is he using it for? Class A, AB, C, or D amplifications?
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