How do you LP wo/caps?

[Magnus Danielson]

From: Paul Perry <pfperry at melbpc.org.au>
Subject: Re: How do you LP wo/caps?
Date: Fri, 28 Jul 2000 10:56:49 +1000

> At 06:13 PM 27/07/00 -0700, you wrote:
> >
> 
> >too much away, has anybody ever seen anything like this 
> >before?
> >
> Miller effect. you have likely synthesised a reasonable 
> capacitor from a Miller effect from the input diode 
> capacitance, and strays. 
> Also there are a couple of poles inside the OTA.

... which does not come from the Miller effect on the input trannies.

I've seen models of op-amps with loads of poles and zeros stuffed in there
in order to model the frequency behaivour, so there is a reason for us to talk
about dominant poles ;)

> I often make a nice sine oscillator from a LMC660, but
> yours seems much more useful! Good one!
> 
> I dont know if you are into SPICE but this wd solve the 
> question of how useful spice is or is not ;-)

Eh, rather, how able he is to use spice for something....

;)

Anyways, most likely are you toying around with the dominant poles... which is
not a bad thing but I bet my horse (I don't own one, so thats fine) that you
should really go into individual trimming on this one, so I would not make use
of it in a commercial product... have you tested temperature stability of
frequency/Q ? Power-supply stability? Do you ever test that BTW? I would not
be supprised if you would find it more sensitive than normal filters.
Good or bad, well, thats another plate...

Cheers,
Magnus