Question about vco capacitor

[capicoso]

Hello. I'm building the vco. And here i have problems finding the silver mica capacitor 1%. So far i found silver mica 270pf BUT +-10% not 1%. NP0 ceramics 220 or 270, or polypropylene. The silver mica one is still the best even with 10% tolerance?
thanks

[isak]

You can use styroflex as well
http://www.ebay.com/itm/Polystyrene-Styroflex-Capacitor-Made-by-Philips-listing-is-for-2-pieces-/271128402472?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item3f20831a28


Q...
What you will be using, the OPA2137P or OPA2137PA?
I want to build the vco as well and I'm not sure about this IC.
The OPA2137P is more expensive then the OPA2137PA, don't know why tho...
Any help will be thankful.

Cheers,
Isak E.

[capicoso]

[isak]

Really?
I have some 442's, I wander what will be the deference using 442's or tl072 like Yves recomands.

EDIT:
Yves, what will be preferred instead OPA2137, TL072 or LF442?


Cheers.

[elmegil]

The question of film vs NP0/C0G caps comes up pretty regularly, and I have never seen any convincing reason why film would be preferrable. I still use them because I have a stock, but the long term plan is to get more stock of the C0G's....

[capicoso]

[yusynth]

Any precision dual AOP will do. The important is that it has a low bias.

Concerning the cap, the important is the temperature coefficient which must be kept low (500ppm maximum), in general silver mica and styroflex are offering that. The 1% tolerance is not really important unless you want to built plenty of VCOs and you want them to behave the same.

[capicoso]

Well my idea would be having various VCOs. If i use NP0 then i think i'll have to match them to 1%. When you say they'll behave different, you mean they'll be tuned differently? Or...?

thanks

[yusynth]

Yes, "tune differently"