Post by thread:[OT] Current Feedback Op-amps

Hi all, I'm looking for a primer on current feedback op-amps. I can't find anything on them in Horowitz & Hill's "Art of Electronics". From diagrams I've seen, it looks to me as if they are hooked up rahter similarly to voltage feedback ones,but I'd like to know how to properly analyze them. I'd like to learn about them in general,but in this specific application , I need an approx. 5 times gain buffer which swings almost rail to rail on +/- 5V supplies (or can handle +/- 30V supplies and swing +/- 5 V) while driving a 100 ohm load (50 ohms back terminated) and provides output short circuit protection, all such that it maintains almost 5 times gain up to 20MHz. I have found a Linear Tech. part (OP681) that seems to fulfill my requirements,but it is current feedback. I am of course willing to consider other parts if anyone has a suggestion. Thanks, Sean | | Sean Breheny | Amateur Radio Callsign: KA3YXM | Electrical Engineering Student \--------------=---------------- Save lives, please look at http://www.all.org Personal page: http://www.people.cornell.edu/pages/shb7 spam_OUTshb7TakeThisOuTcornell.edu Phone(USA): (607) 253-0315 ICQ #: 3329174

I wrote: >20MHz. I have found a Linear Tech. part (OP681) that seems to fulfill my requirements,but it is >current feedback. I am of course willing to consider other parts if anyone has a suggestion. I meant Burr-Brown part, OPA681 | | Sean Breheny | Amateur Radio Callsign: KA3YXM | Electrical Engineering Student \--------------=---------------- Save lives, please look at http://www.all.org Personal page: http://www.people.cornell.edu/pages/shb7 .....shb7KILLspam@spam@cornell.edu Phone(USA): (607) 253-0315 ICQ #: 3329174

try the opamp cookbook. it has a section on current control using opamps, current scaling etc. it should put you in the right direction glen Sean Breheny wrote: > Hi all, > > I'm looking for a primer on current feedback op-amps. I can't find > anything on them in Horowitz & Hill's "Art of Electronics". From diagrams > I've seen, it looks to me as if they are hooked up rahter similarly to > voltage feedback ones,but I'd like to know how to properly analyze them. > > I'd like to learn about them in general,but in this specific applicati on, {Quote hidden}> I need an approx. 5 times gain buffer which swings almost rail to rail on > +/- 5V supplies (or can handle +/- 30V supplies and swing +/- 5 V) while > driving a 100 ohm load (50 ohms back terminated) and provides output short > circuit protection, all such that it maintains almost 5 times gain up to > 20MHz. I have found a Linear Tech. part (OP681) that seems to fulfill my > requirements,but it is current feedback. I am of course willing to consider > other parts if anyone has a suggestion. > > Thanks, > > Sean > > | > | Sean Breheny > | Amateur Radio Callsign: KA3YXM > | Electrical Engineering Student > \--------------=---------------- > Save lives, please look at http://www.all.org > Personal page: http://www.people.cornell.edu/pages/shb7 > shb7KILLspamcornell.edu Phone(USA): (607) 253-0315 ICQ #: 3329174

At 05:03 PM 2/12/99 , you wrote: >Hi all, > > I'm looking for a primer on current feedback op-amps. I can't find >anything on them in Horowitz & Hill's "Art of Electronics". From diagrams >I've seen, it looks to me as if they are hooked up rahter similarly to >voltage feedback ones,but I'd like to know how to properly analyze them. I copied a couple of application notes out of an old Comlinear data book, the description is pretty thorough, and there are lots of good example circuits. A much shortened version of the description: 1. Input stage is a unity gain voltage buffer connected across the inputs of the op-amp- to force V- to follow V+ 2. Amplification is provided by a transimpedance amplifier which senses current delivered by the buffer (above) to the external feedback network, and produces an output voltage such that Vo =z(jf)In, where z(jf) represents the transimpedance gain of the amplifier in V/A or ohms, and In is the current out of the inverting input. > I'd like to learn about them in general,but in this specific application, >I need an approx. 5 times gain buffer which swings almost rail to rail on >+/- 5V supplies (or can handle +/- 30V supplies and swing +/- 5 V) while >driving a 100 ohm load (50 ohms back terminated) and provides output short >circuit protection, all such that it maintains almost 5 times gain up to >20MHz. I have found a Linear Tech. part (OP681) that seems to fulfill my >requirements,but it is current feedback. I am of course willing to consider >other parts if anyone has a suggestion. They are used somewhat like an op-amp, where the op-amp is not as "ideal" as the traditional op-amp, and the CFOA is missing the internal "roll off" capacitor. You can also look for the data sheet to the Analog devices AD811, another CFOA Matt