[sdiy] 1-pole LPF using a differential integrator?

[Aaron Lanterman]

On Apr 30, 2008, at 1:08 AM, Aaron Lanterman wrote:

> The NPN pair driving the differential integrator forms a variable  
> gain integrator with transfer function A/RCs, where A is the voltage  
> gain of the diff pair and R and C are the resistor values used in  
> the integrator. Let's denote wo = A/RC. Now imagine we take the  
> output of this integrator and feed it back into the input with a  
> minus sign. You get something like this:

Actually I think that should be wo = 2A/RC, since we're differencing  
two versions of the same signal with different signs (like in a Moog  
ladder). Hopefully this configuration should have the effect of  
cancelling out the common mode gain of the differential pair.

- Aaron