Testing capacitors.

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Mike H
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#16

Post by Mike H »

Nick wrote:f = 1 / ( 2 * pi * c * r )
Just a note, C in Farads, R in Ohms (so 1uF would be 0.000001)

Another type of 'rule of thumb' I was told years ago was (rightly or wrongly) make the reactance of C some fraction of load R so that signal level across R drops by one seventh at the lowest freq. you want it to pass.

E.g. 1uF > 50k, or permutations thereof with the same ratio.
 
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Paul Barker
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#17

Post by Paul Barker »

Or just open any spreadsheet program and make three rows.

Row 1 column A write Rg Column B (square 1B) = Rg value in K i.e. 100

Row 2 column A write Frequency Column B (square 2B) = Lowest frequency of interest in cycles i.e. 2.

Row 3 column 1 write Capacitor Value= Column B (square 3B) cut and paste the following formula +1000000*((1/B2)/(2.828*B1*1000))

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When building an amp with global feedback work to 1 Cycles


Usual SE DHT diy stuff no feedback anything below 5 cycles

I have all my formulas in this way. I sell you my computer for £1,000. How you think I bang out facts so fast? Don't need five pages of discussion to design my amps. just a quick tip. Not all of the web available downloadable spreadsheet formulas are correct. I make my own from the facts published in text books which have passed peer review editorial checking and have become known reliable electronics sources for their era. Not the self praise of some internet wannabe.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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