[sdiy] LM13600 Gain Question

[jhaible]

> I'm looking at the LM13600 data sheet and fig. 4 (stereo
> volume control) has a formula to calculate the gain given
> Iabc as:
>
> Vout
> ---- = 940 X Iabc
> Vin
>
> Why 940?

I guess that's just the factor you get from Equation (6), applied
to the specific resistor values and supply voltage levels shown
in figure 4.


> Also, with a maximum Iabc of 2 ma. applied to one OTA, this
> circuit can achieve a maximum gain of only 1.88.  So through
> most of it's Iabc range, it's more of a voltage controlled
> attenuator.  Am I whacked here?

You can either decrease the 10k input resistors, or increase
the 10k output resistors to get higher gain.
With the diodes active, you have a current-in, current-out device,
so you just set the resistors to match your desired voltage levels.

JH.



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