Analog Computer Simulation Op-amp Circuit help

Thread Starter

Isaac Tee

Joined Feb 21, 2018
5
Hello there!

I seem to have problems with question 12.55. Unfortunately, nothing of this sort has been covered in my lecture notes and I can't find any comprehensive solutions or explanations on Google. Any help (with an explanation on analog computers) would be greatly appreciated. Thanks all!
 

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MrAl

Joined Jun 17, 2014
8,351
Hello there!

I seem to have problems with question 12.55. Unfortunately, nothing of this sort has been covered in my lecture notes and I can't find any comprehensive solutions or explanations on Google. Any help (with an explanation on analog computers) would be greatly appreciated. Thanks all!
Hello,

Do you know how to handle just one op amp section with one resistor and cap as in your diagram?
That is, just one stage alone without anything else?
 

Thread Starter

Isaac Tee

Joined Feb 21, 2018
5
Hello,

Do you know how to handle just one op amp section with one resistor and cap as in your diagram?
That is, just one stage alone without anything else?
if it's in an active filter configuration, then yes. i'm not too familiar with integral op amps (it wasn't covered in my lectures)
 

MrAl

Joined Jun 17, 2014
8,351
if it's in an active filter configuration, then yes. i'm not too familiar with integral op amps (it wasn't covered in my lectures)
Hi,

Ok well here is a hint then. If the output of a particular circuit is the integral of the input, then the input must be the derivative of the output. This means you can look at a single integrator stage two different ways.

Another hint is then when using the inverting input of an op amp with the non inverting terminal grounded, the inverting input looks like a virtual ground. One important consequence is that any resistor connected to the inverting input acts alone even if there are other resistors connected. That means for that one input the others dont matter. The influence of each input (with their own respective resistors) acts alone and the output is the sum of all the input effects. For example, if we have a 2v input with 2M resistor and a 1v input with 1M resistor, both resistors going to the inverting input, the effect from the 2M resistor and 2v source is independent from the 1v and 1M resistor, so the total input current is just 2/2M+1/1M. This is unlike other nodes where we have to also combine impedances. The name for this is usually referred to as a "summing junction" because it sums the currents caused by two or more inputs. This principle helps when figuring out how the feedback of this circuit combines with the input of this circuit.

The links provided in another post could help you too quite a bit. If you still have difficulty we'll have to do a single stage first then.
 
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