Analysis of Op-amp circuit

[Electric1]

I am analyzing the below op-amp circuit.


my main worry is with the R5 resistor, in absence of R5 and Vin = 10V, Vout= 2.5V(1+10kOhm/30kOhm) = 3.33V which matches exactly with LTspice,

but with R5 in place the voltage at inverting and noninverting is the same and current through R5 is 0 hence the result needs to be same as 3.33V but i could not understand the ramp. what is the significance of R5?

 

[Electric1]

Any help on the purpose of R5 resistor?

 

[danadak]

With - fdbk there is a virtual ground between + and - OpAmp inputs, so not sure why its there.

However there is an input offset present, with drift, but not sure this is what your are seeing.

Maybe examine model to see if input offset is dependent on time or are you just seeing the
finite mathematical accuracy of sim algorithm over the sim time..... Notice that sim seems to
level off just prior to sim end....

You might also see if there is extended accuracy setting in LTC.

 

[Harald Kapp]

@Electric1: This is the same circuit as in your other thread. Please stay within a single thread. I'll lock this one.

Btw_ are you sure this is not homework?
If not, where does the circuit come from.
If it is your design, how did you design this and why do you ask us for the purpose of components?