Bob Cordell's Power amplifier book

We can calculate the nonlinear base current due to Vaf to see if it matches the distortion figures.

Hi keantoken, thanks for contributing some analysis :)

Cordell's BC550C model tells me Vaf is 162 and from experience Hfe is about 500.

Your sums seem to assume that this figure of 500 is measured at 0 V Vce but this won't be the case. Anyway, accounting for the actual value of Vce for this measurement would only make a small difference to your calculations.

54.7nApp total error base current, which we can assume is mostly 2nd harmonic.



57uV error in 1V is 0.0057%. Most of this is still the fundamental though

(emphasis added by me). These two statements do not appear to be in agreement. What am I missing?
 
I'd like to fully agree. But if simulation work is rudely bashed by certain people around here, then one simply has to stay away.

Have fun.

I'm not sure if the earlier comments RE: simulation were being directed at you; certainly I didn't read it that way and thought they were just more general. I view the ability to use "ideal" components in simulation as one of simulation's most powerful benefits. So thank you for your contributions also.

Whilst I would have to agree that in the end, measurement (as long as it's been done properly) is reality, I also agree with Bob that if simulation and measurement disagree to a very large extent, further investigation is required and it is possible that the error lies in the measurement method (this final comment is meant as a general one rather than aimed at anything specific being currently discussed).
 
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I wonder if "Distortion in low-noise amplifiers" by Eric F. Taylor, Wireless World August, 1977
might shed any light on the input current distortion question. We've discussed the article back in
2005 but I've not looked at the article since then. I remember that someone had it in .pdf format.

Found it in .pdf format, in case there is interest: http://www.keith-snook.info/wireles...d-1977/Distortion in low-noise amplifiers.pdf

It seems that the article was taken down, it is still in the index here but the
link no longer works: ~ Scanned and cleaned up Wireless World Articles ~
 
So (I thought) go measure (build something on the realty plane :)).
But... new hurdles pop-up, anyone? what is this difference between I(R1) and Ib(Q1)?
 

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