[sdiy] LM13700/LM13600-based filters

[Antti Huovilainen]

On Mon, 26 Apr 2010, Harry Bissell wrote:

> There are some major issues. One is that if you use the LM13700, the 
> bias of the buffers is preset and may limit performance. In the LM13600 
> the bias is variable with the Gm input, and might feed through to the 
> output.
>
> In all cases, there will be an offset voltage because of the
> voltage drop of the darlington pair. This may not be a problem

Actually, no, there won't be. In a lowpass filter the buffer is inside the 
feedback loop that operates at below cutoff, and thus the only offset is 
due to the OTA input.

Antti

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