The easiest is probably to write equations for all the current into the summing node (whose sum has to be zero).
For example, the current from the output to the sum node will be the output voltage divided by R7 plus the output voltage minus the Zener voltage divided by R8.
I leave the calculation for the input current to the sum node and solving the simultaneous equation, to you.
Make sense?

See post #19.

 

See post #19.

Okay.

 

Here are some simulations.

The first pic is the circuit as is, the second pic is with an added 4.2v zener. We can see that the zener(s) act as breakpoints where the curve changes at the zener voltages.
The 3.2v zener acts as a breakpoint so adding a 4.2v zener and additional series resistor (2k for sharper break than 10k) we add another breakpoint as shown in the second pic "OpAmpDualZenerFeedback.gif".

 

View attachment 183594

what is Vo of this circuit.
When D3 will go in breakdown ?
How do i calculate Vo ?

The output is -10V. It's split in parallel across the two output paths- -3.45V across R8 & D3, and -6.55V across R7. MrAI is correct. However, unless the power-supply can provide -10 to the OpAmp, the result of this circuit int he real-world would be different.

 

The output is -10V.

No.
With +1V input the output is about -6V, as my simulation shows.

 

The output is -10V. It's split in parallel across the two output paths- -3.45V across R8 & D3, and -6.55V across R7. MrAI is correct. However, unless the power-supply can provide -10 to the OpAmp, the result of this circuit int he real-world would be different.

What input do you say produces -10v output?
I calculate +1.65v for that output.

Vout=-1.6-5*Vin when Vin>0.32v

 

Hello,

I thought you guys might like this.
This is a graph of Vout vs Vin (not Vin vs Vout) and it was done that way because it's easy to solve for Vin but hard or maybe impossible to solve for Vout. It was done using conditionals for the two breakpoints -3.2v and -5.2 volts. That equation was then solved for Vin.
The original equation with two breakpoints is shown in the first diagram, then it is rotated -90 degrees and then mirrored. That puts the Vin at the bottom of the graph although some of the numbers are flipped as well, but you could always flip them back

 

View attachment 183592

Hi Guys,
Could anybody explain me, how to analyze the above circuit.
What is out put of this circuit ?
I expect theoretical calculation and explanation ?

Regards,

Petkan:
This is an unity gain follower arranged as peak detector. D1,C3 form a peak detector. The negative half wave charges C3 to peak value, the positive half-wave gets buffered by the unity gain follower (very high input resistance allowing C3 to reach the peak value). The output diode and cap acts as peak detector, holding the peak value after the positive half-wave is over