Hi Team,
I tried to simulate a circuit given as solution for the below problem.(Please find the attached for Question)
I tried to simulate the answer given for the problem(Please see the attached file for solution).
I am not getting the answer as expected after simulation.Sending my simulation file along with this mail.
Could you please tell me where I made the mistake.
Regards
Hari
Hi Hari,
it's funny: The answer presents a new question: How have the resistors to be chosen, so that this scheme can work?
Take care, the output voltage of OPAmp and by this the left side of zener must always be more positive than the right side of zener. This means that the output of OPAmp is always sourcing current. This has two consequences:
1. The output of OPAmp must be able to deliver this current. So, don't take too small resistances.
2. The ratio of resistors is important. The resistors in the feedback loop must be more than four times higher than the resistor which is going to the -25V supply. Why that? Assume the input voltage of circuit is 20V. Then the output voltage of circuit must be -20V. So, across the feedback resistor 20V will drop and across the resistor which is going to the -25V supply 5V will drop. To guarantee that the current in the feedback loop is smaller than the current into the resistor which is going to the -25V supply, the resistors in the feedback loop must be more than four times higher. Only by this the OPAmp output is able to always source current.
Kai
