Re: Beginner's question: NPN common-emitter amplifier setup?
- From: ehsjr <ehsjr@xxxxxxxxxxxxxxxx>
- Date: Thu, 23 Feb 2006 04:48:50 GMT
glennyoon@xxxxxxxxx wrote:
I have done my research and much of what you guys are saying makes
sense!! Thanks!
BTW: How do you set the voltage at the emitter so that it is 0.7 v or
so less than the voltage at the base? I know that the base voltage is
set my some sort of potential divider resistor setup. But how do you
ensure that the emitter will be less than the base?
Glenn
Getting a bipolar transistor to do what you want (within
its capabilities) is all about controlling b-e current,
and there are numerous was to do it, so there is no one
single answer to your question "how do you ensure that
the emitter is less than the base"?
But there is an implication in your question that needs
to be addressed. Your question implies that you may think
the base must always be ~.7 volts higher than the emitter.
You need to think of it a little differently.
The amount of b-e current controls the amount of c-e
current. It could be that you want *no* c-e current,
in which case you would not want the emitter to be ~.7
volts more negative than the base.
What you want to do is control the b-e current and not
have the base *always* ~.7 volts higher than the emitter.
The reason .7 volts is an important number is that
there will be no c-e current until the base voltage is
raised to about .7 volts more positive than the emitter
voltage in the NPN transistor. In a PNP, the base would
need to be about .7 volts more negative than the emitter
for there to be c-e current.
Ed
.
- References:
- Beginner's question: NPN common-emitter amplifier setup?
- From: glennyoon
- Re: Beginner's question: NPN common-emitter amplifier setup?
- From: Jonathan Kirwan
- Re: Beginner's question: NPN common-emitter amplifier setup?
- From: glennyoon
- Beginner's question: NPN common-emitter amplifier setup?
- Prev by Date: Re: Open Source Thermostat and more (Schematics)
- Next by Date: Re: Need Help/Advice about Sound System
- Previous by thread: Re: Beginner's question: NPN common-emitter amplifier setup?
- Next by thread: Re: Beginner's question: NPN common-emitter amplifier setup?
- Index(es):
Relevant Pages
|
