Analyzing an op amp

ScottWang

Joined Aug 23, 2012
7,409
The 0.9V output voltage is right.

How to connecting the batteries to the 741, where is the +9V of battery that it will be connecting to which is the +9V on the circuit, and where is the -9V of battery that it will be connecting to which is the -9V on the circuit.
 

Ron H

Joined Apr 14, 2005
7,063
See image:
http://i1362.photobucket.com/albums/r687/JasonMcG1/Circuit_zps98e971ed.jpg

I have tried to decipher what i think is correct. Using the gain on each amplifier and multiplying it by the voltages i acquired Vout to be +1.9 volts. Need to know if i am correct. Also need to know what to do for part ii. Also where do you connect the battery in this circuit? Any and all help is much appreciated. Thanks.

Jason M
The gain of inverting amplifier = -(9V*(Rf/Ri)) = -(9V * 0.1) = -0.9V
The gain of noninverting amplifier = 9V*((Ri+Rf)/Ri) = 9V*(11/10) = 9.9V.

The +V only 9V, so the output could not reach to 9.9V.
You are both wrong.

Jason, show your work.
 

Thread Starter

JasonMcG

Joined Apr 27, 2013
24
I have renamed the components for easier referencing.
See image:
http://i1362.photobucket.com/albums/r687/JasonMcG1/Ciruit_3_zpsac535a8d.jpg

Amp A: inverting
Gain A = R2/R1 = -0.1
-0.1x9V= -0.9V

Amp B: non-inverting
Gain B = 1+(R4/R3) = 11V
11x0.1 = 1.1V

Amp C: non-inverting 'buffer'
Gain C = 1
1x1.1 = 1.1V

Amp D: 'Summing amp'
G1=-(R7/R5) = +0.9V
G2=-(R7/R6) = -11V
R5//R6
G3=1+(100/9.091) =1+11=12
12x1 = 12V

Therefore Vout = 0.9-11+12 = 1.9V
 

Ron H

Joined Apr 14, 2005
7,063
I have gone through it again and calculated Vout to be 23.9V. Is this the correct value?
If you had an ideal op amp with no limits on output voltage, that would be correct. As jony130 says, the output can never exceed the rail voltages. With a 741, and ±9V supplies, your output will never exceed ≈±8V.

That is either a trick problem, or a very poorly designed one.
 
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