[electric leazenby]

Does anyone here know why 15.39 is used to calculate a phase shift frequency? The chapter is over oscillators. My instructor does not know where 15.39 came from and has offered extra credit if anyone could find out. I would appreciate your help. A google search did not help.

 

[Meadow]

Does anyone here know why 15.39 is used to calculate a phase shift frequency? The chapter is over oscillators. My instructor does not know where 15.39 came from and has offered extra credit if anyone could find out. I would appreciate your help. A google search did not help.

What application are we talking about? Phase shift as in a phase shifting power transformer?

 

[tsteverose]

Is this for a Physics class, or are you in some type of ET school? Either way, we would need more info to the subject matter.

 

[electric leazenby]

It is electronics being taught in my third year njatc apprenticeship class for the IBEW. Thank you for your time.

 

[lefleuron]

Going back a LOOOONG way I seem to remember using the reciprocal of 15.35

as a baseline frequency for figuring out feedback. I dont remember if it was

for positive or negative feedback though.

Didnt this have something to do RC networks and 1/15.35 and.....

Too long ago friend, and not something I ever use. Sorry.

 

[tsteverose]

Going back a LOOOONG way I seem to remember using the reciprocal of 15.35

as a baseline frequency for figuring out feedback. I dont remember if it was

for positive or negative feedback though.

Didnt this have something to do RC networks and 1/15.35 and.....

Too long ago friend, and not something I ever use. Sorry.

I think you nailed it. It has to do something with an RC Network. It's been along time for me as well. To the op, please post a question and formula where this is being used. I'm better a reverse math, than I'm at remembering things. :laughing:

 

[electric leazenby]

Yes it does have to do with RC networks. I will post the question when I get home. I do not want to waste your time anymore till I can see my book. I think the formula was 1/15.39RC. The math was not a problem, but no one knows where the 15.39 comes from. Again I will check when I get home and post the question. Thank you all.

 

[bobelectric]

Sounds like a caper for www.mikeholt.com

 

[electric leazenby]

The phase shift components are .02 microfarads capacitors and 15 kilo ohm resistors. At what frequency will the network produce a phase shift of 180 degrees? Is the workbook question. The answer is 216.5 Hz
My book "semiconductors" gives the formula 1/15.39xRC.
The book does not give where the constant 15.39 comes from and no one seems to know. My instructor says it is brought up every year. That is why he is giving extra creditifanyone can find it. Thank you all.

 

[Aussielec]

http://www.electronics-tutorials.ws/oscillator/rc_oscillator.html

Scroll down the page to "Basic RC Oscillator Circuit".

 

[lefleuron]

Sounds like a caper for www.mikeholt.com

Yeah, right.:laughing:

 

[azgard]

I hate when book's do what the op is dealing with. Some of the professor's I had that were active engineer's usually made it a point to at least show how formula's were derived when given. Really helps with understanding what the hell is going on then just taking random numbers and memorizing them.

 

[lefleuron]

Well,

seeing as I cannot find the answer and I cannot find my "the art of electronics"

book, I am going to suggest you go to one of the Electronic Engineers forums

and ask. One of those geeks-on-a-stick is going to know.

But be prepared, the answer may be much worse the then any math formula

you have yet encountered. :laughing:

 

[electric leazenby]

Thank you all very much. I strive to do well in school and on the job. I can use the extra credit. We have gone through semiconductors at a fairly fast pace and it has been hard to grasp all of it. I have done well, but I appreciate the points and all the help. Have a good Sunday and upcoming week.

 

[Ultrafault]

Yeah it is 2pi times the sqrt of 6.

You can see the formula it is drived from on the phase shift oscillator wikipedia page.

Now ask me why the sqrt of 6.