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Problem with this opamp

I don't find correct Req value in this opamp configuration:
http://img46.imageshack.us/img46/1848/opampnr3.png
If i don't consider Ib and define:
1)Va=voltage across R2
2)eo=Ip*Req
Va=RfT*Ip=(R2/(R2+R1))eo, so e0=Ip*(RfT*(1+R1/R2))
This result is right if Rft>>R1, but in general Req=Rft+R1+(Rft*R1)/
R2: so it is wrong...can you help me?
I have another question:i'm looking for a good book about systematic
methods for the study of networks with active and passive
components...i'm looking for a book that give to me ability of analyze
electrical circuits in simple and quickly way...
Thanks
 
I don't find correct Req value in this opamp configuration:http://img46.imageshack.us/img46/1848/opampnr3.png
If i don't consider Ib and define:
1)Va=voltage across R2
2)eo=Ip*Req
Va=RfT*Ip=(R2/(R2+R1))eo, so e0=Ip*(RfT*(1+R1/R2))
This result is right if Rft>>R1, but in general Req=Rft+R1+(Rft*R1)/
R2: so it is wrong...can you help me?
I have another question:i'm looking for a good book about systematic
methods for the study of networks with active and passive
components...i'm looking for a book that give to me ability of analyze
electrical circuits in simple and quickly way...
Thanks

silusilus,
The exact equation is Rfeq = Rft + R1 + (RftR1/R2). No assumptions
are necessary.
A classic book on circuit theory is "Introductory Circuit Theory" by
Ernst A Guilleman. It's long out of print, but is readily available
used. A quick Google search will provide lots of sources. I got mine
on Ebay.
Regards,
Jon
 
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