Common emitter amplifier

[Chr1s]

Can anyone explain to me why my output signal from the collector of CME amplifier is 180 degrees out of phase from my input signal. Input signal is 2v pkpk done wave at 1khz?

 

[Bluejets]

Basically, as the transistor turns harder on due to more base bias, the collector goes towards ground.

 

[Audioguru]

I wonder why you did not look in Google? All the articles say that a common emitter transistor inverts a signal which means its output is 180 degrees out of phase from its input.

 

[Syncopator]

The signal at he collector is inverted. It is not shifted in phase. And no, they're not the same thing.

 

[Audioguru]

The signal at he collector is inverted. It is not shifted in phase. And no, they're not the same thing.

Wikipedia says that an inverted signal has a 180 degrees phase shift. I agree.

 

[LvW]

Wikipedia says that an inverted signal has a 180 degrees phase shift. I agree.

Wikipedia is not he bible. Several examples can reveal wiki`s errors.
I think, phase inversion are identical to a 180deg phase shift for sinusoidal (periodic) signals only.
However, ther are also non-periodic applications.

 

[Syncopator]

Take a look at this www.davidbridgen.com/pol.htm

(That link doesn't seem to work - just type it in to your browser.)

The reference to the source is no longer valid, but the wisdom in the article is.

Some time ago I intended to put together a fairly simple circuit on a breadboard to demonstrate the fallacious inversion/phase shift belief.

I don't think I'm going to bother now. I used to be very active on several electronics forums but I got fed up to the back teeth with people arguing simply to win arguments so I withdrew from them.

 

[Bluejets]

Well I'd have gone with Audioguru as I don't believe the Op actually wants to get a shuttle into Lunar orbit just yet.

 

[Audioguru]

The article talks about the phase (and very important delays) caused by speaker placement and speaker polarity. A speaker that is close to you produces sounds before another speaker that is farther away so the outputs do not cancel properly when they have a 180 degrees phase difference.

 

[Bluejets]

I originally imagined there may be some reference to clipping or overdriving causing distortion.
Either way, I go with your 180 for the OP.

 

[Audioguru]

I originally imagined there may be some reference to clipping or overdriving causing distortion.
Either way, I go with your 180 for the OP.

Clipping has nothing to do with phase or polarity. Clipping occurs when an output level is attempting to go higher than is possible. A transistor without negative feedback produces severe distortion at higher levels (but not clipping).

 

[Bluejets]

Well aware of that. My point being there may have been some comparision between in and out other than inversion.

 

[Audioguru]

Here is the typical distortion (about 40%!) of a transistor with a high output level because it has no negative feedback, but it is not clipping: