Hello,
For a school project I need to know how a differential amplifier works. I watched several videos on it and tried to understand them, but there's a few things that are just very unclear to me. For reference, I'm going to talk about the circuit below:
The problems that I encounter are the following:
1. The differential amplification formula
The formula above, I don't understand what they mean by Vout. Do they refer to Vout in the reference image I showed above? Because in another nearly identical formula, it's stated another way:
These are basically the exact same formulas, except Vout has been replaced for (VoutVout'). How does this work? What is the actual output voltage on a differential amplifier? When I analyze circuits with a differential amplifier embedded into it, I only see one output. However, on the reference image there's two outputs. How are these two outputs connected so that they form one output? And how are they connected so that the output voltage is equal to the difference between Vout and V'out?
2. The 'normal mode'
So, for the normal mode the formula is as following:
or
First of all, how are these two formulas connected? How is Vout in the first formula equal to Vout+Vout' in the second formula?
Then the second question I have is; how do you make Acm a small number? Because I read that to make a differential amplifier, Acm should be very small, and ideally 0. How could you make Vout very small, while keeping Vin and Vin' high?
3. Inverting and noninverting input.
I read that differential amplifiers have inverting and noninverting inputs, but I don't really understand how one input can be inverted in the reference image. It would make a lot of sense if one input was inverted, since it would probably solve a lot of the troubles I'm currently having but I can't seem to find any explanation that uses formulas/math to explain how one input (for example Vin2) can be inverted.
Sorry for all this rambling, but I have been struggling to find any explanation to make differential amplifiers more clear to me. Thanks a lot in advance for helping me out!
For a school project I need to know how a differential amplifier works. I watched several videos on it and tried to understand them, but there's a few things that are just very unclear to me. For reference, I'm going to talk about the circuit below:
The problems that I encounter are the following:
1. The differential amplification formula
The formula above, I don't understand what they mean by Vout. Do they refer to Vout in the reference image I showed above? Because in another nearly identical formula, it's stated another way:
These are basically the exact same formulas, except Vout has been replaced for (VoutVout'). How does this work? What is the actual output voltage on a differential amplifier? When I analyze circuits with a differential amplifier embedded into it, I only see one output. However, on the reference image there's two outputs. How are these two outputs connected so that they form one output? And how are they connected so that the output voltage is equal to the difference between Vout and V'out?
2. The 'normal mode'
So, for the normal mode the formula is as following:
or
First of all, how are these two formulas connected? How is Vout in the first formula equal to Vout+Vout' in the second formula?
Then the second question I have is; how do you make Acm a small number? Because I read that to make a differential amplifier, Acm should be very small, and ideally 0. How could you make Vout very small, while keeping Vin and Vin' high?
3. Inverting and noninverting input.
I read that differential amplifiers have inverting and noninverting inputs, but I don't really understand how one input can be inverted in the reference image. It would make a lot of sense if one input was inverted, since it would probably solve a lot of the troubles I'm currently having but I can't seem to find any explanation that uses formulas/math to explain how one input (for example Vin2) can be inverted.
Sorry for all this rambling, but I have been struggling to find any explanation to make differential amplifiers more clear to me. Thanks a lot in advance for helping me out!
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