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Formula for frequency of gate oscillator?
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Formula for frequency of gate oscillator?

by shobley on Sat Apr 04, 2009 12:13 pm

Anyone know the formula for a NAND gate oscillator, like here:

http://thereminvision.com/sensors/schematic-10.jpg

In the top left corner, there is one with a 20pF Cap and a variable 20K resistor.

Anyone know how to express the frequency in R and C?

[I bet 0.693 comes into it somewhere... :D ]

Steve
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Re: Formula for frequency of gate oscillator?

by shobley on Sat Apr 04, 2009 9:51 pm

Turns out the datasheet had it all the time...

At 5v I worked it out to be f = 1/ (RC ln(3.451))
= 1/(R*C*1.238)

So 0.1uF cap and 100K resistor gives 80.77Hz at 25C and 5v supply.
http://www.stephenhobley.com
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