Ive been stuck for a couple of days now trying to build an inverting op amp circuit using a 741 opamp. I don’t understand why I am not getting the results I expect, which according to theory should be a gain of -2.2.
I am currently a student in electronics engineering; and I have read up on op amp operation which all seems fairly simple, in theory. I understand that the inverting op amp circuit feeds back a large portion of voltage back to the input, putting a muzzle on the large gain of an op amp, and that the inv and non inv inputs will do anything they can to equalize the voltage between the inouts, i.e make it 0 potential difference.
I think I also suffer from a poor understanding of ground in circuit diagrams; as I understand ground (in a circuit), it means a point which is at a 0 potential with ref to another specific point…. In the case of my circuit then, then non inv input is grounded at 9v. I read that a floating input can cause issues; and that outputs can be unpredictable, I have also tried tying the non inv input together at 0v and 9v, but this puts 9v + POT across the inputs.
From the circuit attached here are a sample of results:
Vin Vout
0.0v 8.75v
1.94v 4.34v
and @ 3.5v I presume the opamp saturates, as the voltage between the inv and non inv inputs starts to stray away from 0 and the out remains at 1.5v from this point, until the input reaches max.
The above readings were taken with a supply of 16.98v
Ive attached a circuit diagram and a picture of my effort, Id really appreciate a shove in the right direction here, if only to save my sanity.
A quick run down of the circuit photo:
The lower ground rail on the bread board is where ive grounded the non inv input, pot is also grounded here. Yellow cable is the input, via a voltage divider to the output. The red cable reaching over to the upper ground rail is the output.
I am currently a student in electronics engineering; and I have read up on op amp operation which all seems fairly simple, in theory. I understand that the inverting op amp circuit feeds back a large portion of voltage back to the input, putting a muzzle on the large gain of an op amp, and that the inv and non inv inputs will do anything they can to equalize the voltage between the inouts, i.e make it 0 potential difference.
I think I also suffer from a poor understanding of ground in circuit diagrams; as I understand ground (in a circuit), it means a point which is at a 0 potential with ref to another specific point…. In the case of my circuit then, then non inv input is grounded at 9v. I read that a floating input can cause issues; and that outputs can be unpredictable, I have also tried tying the non inv input together at 0v and 9v, but this puts 9v + POT across the inputs.
From the circuit attached here are a sample of results:
Vin Vout
0.0v 8.75v
1.94v 4.34v
and @ 3.5v I presume the opamp saturates, as the voltage between the inv and non inv inputs starts to stray away from 0 and the out remains at 1.5v from this point, until the input reaches max.
The above readings were taken with a supply of 16.98v
Ive attached a circuit diagram and a picture of my effort, Id really appreciate a shove in the right direction here, if only to save my sanity.
A quick run down of the circuit photo:
The lower ground rail on the bread board is where ive grounded the non inv input, pot is also grounded here. Yellow cable is the input, via a voltage divider to the output. The red cable reaching over to the upper ground rail is the output.
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