How can I make an Op Amp circuit with changeable voltage(MOSFET) for driving 12V & 24V servo motors?
There’s a lot to unpack in your question. Can you take a step back and describe at a high level what you want to do (other than simply drive a motor)?
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Why? You can find relatively cheap hobbyist drives. What exactly is the application that would require a cobbled together servo driver.
Also a side note: if you are looking to do things lower cost why the server motor instead of stepper motors. Open Loop isn’t ideal, but it works for a lot operations.
edit: My original comment was a bit hyperbolic without usable content
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Are you wanting to control your servo using an analogue voltage? If so, where is this analogue voltage coming from? A sensor? A potentiometer?
If you want to turn a knob to control the servo, a servo tester might do the job as long as it works with the servo supply voltage you are using. That might be easier to get locally in Turkey than the device that @Camren provided the link for.
Actually this is a task that I should complete and these are the all informations that given to me.
I should make this circuit as a task and a circuit that will handle all these features is enough for me.
It’s a DIY project and I want to control my servo using digital voltage.
The more specific and detailed you can be about what you want to do and need help with, the more helpful we can be.
Which servo do you want to control? Do you already have parts on hand for this project? Do you have a schematic for what you want to build, or do you need help designing that too?
Sigh. If you don’t understand the problem, neither will we.
First, learn the kind of waveform that controls a servo, and how the waveform needs to look for a specific result. THAT will be an eye-opener for you. Don’t do ANYthing else until you understand this, as your question clearly shows you don’t.
Second, why a MOSFET? These are often for high power, which does NOT describe a servo’s control input. An op-amp can drive this directly.
Third, why an op-amp? As an oscillator maybe? Not sure how this will even come close to accomplishing the task.
Get learning before you ask again. But then, we will be happy to explain in great detail.
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Are you looking for help with a school assignment? If so, you may be better off asking one of the teachers or professors for assistance. As Don stated below, you have not given sufficient information about your problem for anyone to give you any help.
If this is a DIY project and not to be a commercial product, you should not be needing to hide trade secrets. You need to provide much more information to get meaningful help. What voltages? What timing? What waveform? What servo? etc.
Nope, it’s my team’s assignment.
Could you ask whoever gave you the assignment for help, or at least some more details?
Pink,
The people here are trying to understand your application. If your team is wanting to use a commercial servo unit like one of these…https://www.servocity.com/servos/futaba-servos then they are driven by a PWM hobby signal and around 5 volt power supply. The RoboRio has outputs designed to drive these directly.
The term “servo” has many meanings to those of us in electronics. Generally it means a motor that is driven by a motor driver and sends feedback to a motor control circuit. The servos listed above have that built in. When you send a PWM to the servo, it moves to a position where is it commanded by the PWM input and the servo internal electronics makes sure it stays where commanded.
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you’re right, it’s because of my lack of information; i’m just a rookie. but thanks, it helped 
That’s what are here for just ask. We want to help.
Al
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What is it supposed to do?
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it should provide a voltage change between 12V - 24V
You want to switch your motor between 12V & 24V?
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