[sdiy] Some thoughts about ladder filter circuit

[Simon Brouwer]

Ian Fritz schreef:
> At 10:59 AM 12/12/2008, David G. Dixon wrote:
>> General question: Are these arrays suitable for VCO expo circuits?  
>> They're
>> certainly cheaper than super-matched pairs and quads!
>
>
> The best bet for NPN pairs right now is the supermatched LM394, which 
> Futurlec is selling for an incredible $1.80.  I've said it before and 
> I'll say it again: Everybody should stock up on these.
An excellent bargain indeed. I wonder how long it will last.
>
> I've used the CA3083 in many projects.  The log conformance is *way* 
> better than for the 3046, namely Re = 1.3 Ohm vs. 5.0 Ohms.  The 3046 
> is pretty far down on the list for expo converters.
Thanks for the tip, and Farnell has this part as well.
(they have LM394 as well by the way, metal can, for 15.25 euro apiece...)

I think for the ladder filter I'll go with my hand matched transistors, 
glueing them together and in combination with a tempco resistor. If 
necessary (but I don't expect so) I can always replace them with a 
proper dual transistor.

-- 
Vriendelijke groet, 
Simon Brouwer. 

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