Transfer Funtion of the given circuit ?
1 Attachment(s)
Hi,
Please give me the transfer function of the following circuit. Where R1,R2,R3,R4 and R5 are not equal. 
How many marks will your teacher give me for the answer?

Quote:

Just remember that the voltages at inverting and noninverting inputs are equal, that the current flowing into the inverting and noninverting inputs is zero, and it will be pretty easy to set up the basic equations to solve for Vo/Vi.

it actually "safer" to explicitly include op amp gain "A" and derive the equations
you can always take the limit as A goes to infinity later  but by assuming it from the start you may save a term or two in the calculations or you may have your solution "blow up" from the infinity you are implicitly carrying around the op amp Howland current source is a favorite nasty problem set for those not understanding the "null injection" implicit infinity 
What method do you think is best for solving this problem, and how far along did you get?
Dale 
@DF96
I am not a student in any institute so do not expect any Marks. @SY, jcx Thank you, I solved it using superposition theory. R1 and R2 forms voltage divider for NonInv voltage. R3RD forms Rg and R4 forms Rf. So NonInv, Inv output voltage will be Vninv = V1*[R2/(R1+R2)]*[1+{R4/(R3RD)}] Vinv = V1*(R4/R3) Vout = Vninv + Vinv 
Would you not want Vout in terms of V1 ?

Quote:
I'm not certain that your result is correct. I would expect to see two simultaneous equations involving Vin and Vout, which you then invert to get Vout in terms of Vin. What is RD? 
Sorry, R5=RD (In practical circuit R5 will be variable resistor e.g. JFET or LDR)
I've verified the equation with LTSpice. If you any other equation/solution please post that. 
All times are GMT. The time now is 06:24 AM. 
vBulletin Optimisation provided by
vB Optimise (Pro) 
vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright ©19992016 diyAudio