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Can anyone help me set-up my equations for the closed loop gain of this circuit? It's been a while since I've done the calculations and would like to brush up on it. Thanks for the help.
Jony130,
Upon examining your AC derivation, I see you are correct about V2 after all. Z5 will have no voltage across it and no current will exist in it, so Z5 can be removed from the circuit. The + input of the opamp is connected to ground through Z2 with no current or voltage across Z2, so the + input can be connected directly to ground. That leaves V2 = -Z1/Z3 as you have derived it.
Ratch
wuchy143,
Didn't you ask the same question here on 8/26/2011? https://www.electro-tech-online.com/threads/op-amp-gain.121268/
Didn't I answer half of your question by calculating the DC gain of V1? I also asked you if you needed the AC gain of V2, but you did not answer. Have you noticed yet that you have V4 hooked up backwards? Are you aware that the V1 input is going to raise the output to 13.648 volts DC as I stated before? That does not leave much room for the AC voltage V2 to affect the output before it runs into the +15 volt rail. Are you aware of that? Again I ask, do you really need the calculation for the AC input V2?
Ratch
hi,
Assume that V2 =0v
The Inverting gain is 75k/20k = 3.75
this means the Non Inverting gain is 1+3.75 =4.75
The 4.096v voltage is divided down by R4 and R2 to 2.87V
So the OPA output due to the non inverting input will be 4.75 * 2.87v = 13.6V
If you now make V2 = +1V , due to the inverting gain of 3.75 that will drive the OPA down by 3.75 * 1v ie 3.75v
So the net output from the OPA is 13.6v - 3.75 = ~ +10V
If you made V2 = 2v , then the OPA output would be 13.6V - 7.5V = +6.1v
I have rounded the values for simplicity
hi
This is a simple circuit often used with a PIC for ADC projects.
The Vsig can swing between +/-2.5V and pin 1 has to swing from 0V thru +5V.
The second half of the LM358 is used to generate a Vref for the PIC's ADC, if required.
Use a LM358 OPA in LTS
Post your LTspice asc files when you need help with LTS circuits.
Looks as though there a pdf upload problem, tried again , no luck.Sweet. Thanks. Though, when i click on it it shows nothing. I think it might be a dead link?
Hi All,
Can anyone help me set-up my equations for the closed loop gain of this circuit? It's been a while since I've done the calculations and would like to brush up on it. Thanks for the help.
Vout=-(Ao*(s*C2*E2*R1*R2*R4+E2*R1*R4-s*C1*E1*R1*R2*R3-E1*R2*R3+E2*R1*R2-E1*R1*R2)*(s*C3*R5+1))/(Ao*s^3*C1*C2*C3*R1*R2*R3*R4*R5+s^3*C1*C2*C3*R1*R2*R3*R4*R5+Ao*s^2*C2*C3*R2*R3*R4*R5+s^2*C2*C3*R2*R3*R4*R5+Ao*s^2*C1*C3*R1*R3*R4*R5+s^2*C1*C3*R1*R3*R4*R5+Ao*s*C3*R3*R4*R5+s*C3*R3*R4*R5+s^2*C2*C3*R1*R2*R4*R5+s*C3*R1*R4*R5+Ao*s^2*C1*C3*R1*R2*R3*R5+s^2*C1*C3*R1*R2*R3*R5+Ao*s*C3*R2*R3*R5+s*C3*R2*R3*R5+s*C3*R1*R2*R5+s^2*C2*C3*R1*R2*R3*R4+s^2*C1*C3*R1*R2*R3*R4+Ao*s^2*C1*C2*R1*R2*R3*R4+s^2*C1*C2*R1*R2*R3*R4+s*C3*R2*R3*R4+Ao*s*C2*R2*R3*R4+s*C2*R2*R3*R4+s*C3*R1*R3*R4+Ao*s*C1*R1*R3*R4+s*C1*R1*R3*R4+Ao*R3*R4+R3*R4+s*C3*R1*R2*R4+s*C2*R1*R2*R4+R1*R4+s*C3*R1*R2*R3+Ao*s*C1*R1*R2*R3+s*C1*R1*R2*R3+Ao*R2*R3+R2*R3+R1*R2)