EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: haseeb zaib on November 03, 2021, 10:53:44 am
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Hi, I was reverse engineering a circuit for learning purposes and I came across this strange configuration of op-amp. I want to ask, what is the purpose of these diodes? (please explain little bit) are they being used to stop feedback current/voltage ? I was looking at log opamp but it seems to me this is something different.
I have also ran this circuit in ltspice but I still don't understand it.
on inverting input the voltage could vary as shown in image, but on non-inverting input the voltage is being given by voltage divider which equal to 5V-5.1V
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Hi, I was reverse engineering a circuit for learning purposes and I came across this strange configuration of op-amp. I want to ask, what is the purpose of these diodes? (please explain little bit) are they being used to stop feedback current/voltage ? I was looking at log opamp but it seems to me this is something different.
I have also ran this circuit in ltspice but I still don't understand it.
on inverting input the voltage could vary as shown in image, but on non-inverting input the voltage is being given by voltage divider which equal to 5V-5.1V
I have seen a similar schematic, but that only used one diode.
The idea is to produce an amplifier with a non-linear transfer characteristic.
Back in the day, it was common to use an array of diodes to obtain such a characteristic for video "gamma correction" circuits.
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It's an inverting amplifier, with a gain of 10, with the input and output referenced to 5V.
VOUT = 5+(5-VIN)*10
D1 and D2 limit VOUT to two diode drops below 5V.
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thanks alot, for taking the time and doing this simulation
I understood it way better. In the actual circuit, the voltage was also limited to around 4V, similar to it was in a simulation. when I removed the diodes it went to 0 volt.
thanks once again