[sdiy] Ladder filter analysis

[Magnus Danielson]

Tim,

Remember that control is current and signal is voltage.
It's a clever design indeed. Matching of transistors reduces the common 
to differential conversion that would cause CV feed through.

Oh, any such feed through would be temperature dependent, just to make 
it more fun.

Cheers,
Magnus

On 07/07/2014 07:19 PM, Tim Ressel wrote:
> Hi,
>
> I was talking to a guy who was trying to eliminate control voltage feed through on a filter when it dawned on me: the differential nature of the Moog transistor ladder filter design eliminates CV feed through. The audio is balanced on the two sides of the ladder but the current is common mode, so it gets cancelled at the differential amplifier.
>
> Moog really was a clever guy.
>
>
> Tim Ressel
> Circuit Abbey
> 503-750-9331
> timr at circuitabbey.com
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