Emulate logarithmic potentiometer via passive components?

Thread Starter

k1ng 1337

Joined Sep 11, 2020
121
Hi can this be done? I found some information on turning a linear trimpot into log with the help of some resistors but the equations and circuit diagrams were not given.

Regards,
 

MrChips

Joined Oct 2, 2009
24,626
Use the linear pot to drive an LED which then shines on a LDR (light dependent resistor).
You will need to experiment with it to get the desired response.
 

Ian0

Joined Aug 7, 2020
3,766
There's quite a long section in Doug Self's book "Small Signal Audio Design". I'll scan a few pages if you don't have access to it.
 

crutschow

Joined Mar 14, 2008
28,206
Below is the LTspice simulation of the referenced circuit for a 100kΩ linear pot with three different values of R2.
The log curve (second plot) would be a straight line for a perfectly log response.

1626028151318.png
 
Top