# Calculating an equation to fit a voltage range to log scale

Discussion in 'The Projects Forum' started by sindre jacobsen, Jul 24, 2019.

1. ### sindre jacobsen Thread Starter Member

Apr 1, 2019
40
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Hello
I am currently trying to fit a voltage range to an output of a antilog circuit I will be designing.
Here are some of the details:
At 2V output on the antilog amp, the input is 2.85V. At a point 7 dB lower, the output is 0.893 V, while the input is 2.2V.
Anyone who got any ideas on how to attack this problem? I am currently thinking of trying to reparameterize the input so that the output is in the form of 10^u, where u is proportional to the input voltage.
Hope anyone can help.
Thanks

2. ### MrChips Moderator

Oct 2, 2009
19,135
6,150
You have provided two data points.
You can fit an infinite number of models to two data points.
We may be able to provide some assistance if you provided more data points. More would be better than few.
Four data pairs would be the minimum. Ten points would be much better.

3. ### sindre jacobsen Thread Starter Member

Apr 1, 2019
40
0

Went a little overboard with the points, but wanted to try forming an equation with the axis-intersect, but the slope of the equation did not fit...

4. ### sindre jacobsen Thread Starter Member

Apr 1, 2019
40
0
Thanks for providing me with an "aha" moment!
Figured out the equation: Vctrl = 0.05797*10^(Vshape/1.854) ... If anyone was wondering

Jan 18, 2008
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