opamp selector

I always used Towers... I haven't had my hands on this for years now but it was pretty much what you ask - a telephone directory, paramters across the top (both pages) chips down the side - made it realy easy to select a piece... sometimes you'd find just what you were after and it'd be sunnik like $100 10+ eek!

colin a écrit :

Cheap enough to buy by the truck load? Well, it depends, but the OPA228/2228 will fit the bill on all your other criteria.

the

turns

cheap

as

Yes thanks that looks quite good, 1 quid from Farnell, only problem is its minimum gain of 5, the opa227 is unity gain stable but only 8mhz, from the same table there is 180mhz device but input bias is 2ua wich is quite high.

Colin =^.^=

Hello Colin,

Digikey has just about the best search engine of all of them. Just key in "opamp", then narrow down the search parameters to what you want. Hold the shift key for whole ranges.

Unfortunately even the Digikey search has one serious flaw. It does not let you sort by price. But once you have it narrowed down to a few pages it's easy to scoot the pane to the right and scroll through the prices.

This will also let you avoid stuff that's low in stock or out.

the

turns

doesnt seem that good to me or am I missing something ? doesnt let me specify GBW of >=30mhz for example. doesnt even tell me what the GBW is unless I select a part and go look up the data sheet or catalogue page. I can select high speed or wideband but what do they call high speed ?

RS and Farnell seem to have better search engines.

Colin =^.^=

Hello Colin,

Ok, with so much data detail you need to go to the mfg sites. TI is pretty good and lists prices. So does AD. But you will be hard pressed to find 30MHz GBW in view of your other requirements such as 30V VDD,

The OP467 might come close but it'll cost your around $5 for a quad.

up

Thanks, Il keep looking, but the 100R+1nf are in series, Im not sure this is such a demanding load, anyway its just a filter before the vco, and the signal isnt changing much just needs to be stable.

I could do it with a couple of transistors I gues. but I think il get a bunch of OPA228 as recomended by Fred and keep the gain at 5, they actualy look pretty darn good, even specifies 10% overshoot with 1nf load.

TI like many sites is annoying as I have to specify what its use is, ie. I would never have described this as an audio application !

Colin =^.^=

Hello Colin,

If it can be done with a couple of transistors I would do that. Those designs have a much better longevity.

Yeah, that's a nasty habit of the new generation of marketeers. The worst was when they called stuff "Excalibur" and nobody had a clue where to look. TI's site has deteriorated a bit but it's still quite good. They list a category under opamps that says "Greater than 50MHz". Also, they let you list all opamps they've got and then order them by GBW or whatever you like.

The opa2277 dual is a grand part, and the A version is much cheaper than the LT1124 I've been using.* I see all the distributors have plenty of the miniDIP package in stock, but are sold out of the soic package, so I'll have to stick with the LT1124 for now. For example, Mouser shows 1,200 on order but with a 11/27/2006 Estimated Ship Date. TI's site shows the opa2277ua with >10k in process for next 29 Jan. Yep, a popular part, insufficiently produced and badly backed up.

• The OPA2277 is spec'd at 3nV noise, whereas the LT1124 is 2.7nV, which is 10% better! Guess that's why LTC gets the big bucks. :-)

thanks, Farnell have the single in stock but not the dual 2228, Ive found a faster part ad8034, only 24v but single supply rail to rail op. shame about the input diodes .. maybe you might not like the higher noise but still good enough for my app.

Colin =^.^=