Inverting operational amplifier circuit won't work

AI Thread Summary
The discussion centers on troubleshooting an operational amplifier circuit using a 741 op amp, where the expected output voltage is not achieved. The user is experiencing an output of 0.98 V instead of the anticipated amplified voltage, and when using an LF356N, there is no output at all. Key issues identified include incorrect power supply connections, as the user is only achieving ±9 V instead of ±18 V, and a lack of proper grounding in the circuit. Additionally, the circuit configuration is mistakenly identified as an inverting amplifier when it is actually a non-inverting amplifier, affecting the gain calculation. Proper connections and adjustments are necessary to achieve the desired circuit functionality.
gothloli
Messages
37
Reaction score
0
I'm making a simple circuit on the breadboard with a 741 op amp. The feedback resistor is 150 kohms, and the input resistor is 100 kilo ohms, means the gain is 1.5. The input voltage is about 5.33. The power supply is ±18 V. For some reason the output voltage is 0.98 V instead of the amplified voltage. Also when I try the LF356N it doesn't show any output voltage at all.

Below is a picture of my circuit
 

Attachments

Engineering news on Phys.org
I can only see three batteries. How are you getting +/- 18 volts?

How are you getting 5.33 volts input? I can't see any divider resistors. I would make this 1 volt for test purposes anyway.

The red wire on the top battery doesn't seem to go anywhere.

Are you using this circuit?

images?q=tbn:ANd9GcQD70c1nUYza0Ed6zb6IPRKS1YZSqSrOaxcPkzstrbafsl0wpMe.png
 
yah I'm using that circuit.
But the battery I used for the input signal is 5.33 because I burnt it out, because I don't have 1.5 volt batteries around
 
Do you have a meter?
 
I don't see any connection between the midpoint of the two supply batteries, pin 3 and your input's "zero" side. Those three things need to be connected together.
As has been pointed out, your supply only seems to be +/-9V. That should be just about enough though.
 
gothloli said:
yah I'm using that circuit.
But the battery I used for the input signal is 5.33 because I burnt it out, because I don't have 1.5 volt batteries around

No, you're not using that circuit (inverting amp). You're using this circuit. Its a non-inverting amplifier. Gain = 1 + R2/R1 ( = 2.5 in your case)

op-amp_basic_non_inv.gif


Also give the circuit a common ground by connecting the middle of +-18V battery to the negative terminal of your input. (i.e. at the other end of the resistor you took out from pin 2)
 
gothloli said:
I'm making a simple circuit on the breadboard with a 741 op amp. The feedback resistor is 150 kohms, and the input resistor is 100 kilo ohms, means the gain is 1.5. The input voltage is about 5.33. The power supply is ±18 V. For some reason the output voltage is 0.98 V instead of the amplified voltage. Also when I try the LF356N it doesn't show any output voltage at all.

Below is a picture of my circuit

I look at you breadboard. The top battery is supposed to be the input voltage. The black wire is connected to the 100K which connect to pin 2 as input. Problem like Vk6kro said, the red wire of the battery is not connected to the breadboard! If I see you picture correctly, you are not going to get anything meaningful out of this. I can't see where the clip on the black wire goes to as your picture don't show. You need to have connection to the ground reference to establish the potential. The ground reference is the junction of the red wire of the lower battery on the left side and the black wire of the lower battery on the right side. You have no connection of the ground reference to any other points.
 
Last edited:
vk6kro said:
I can only see three batteries. How are you getting +/- 18 volts?

How are you getting 5.33 volts input? I can't see any divider resistors. I would make this 1 volt for test purposes anyway.

The red wire on the top battery doesn't seem to go anywhere.

Are you using this circuit?

images?q=tbn:ANd9GcQD70c1nUYza0Ed6zb6IPRKS1YZSqSrOaxcPkzstrbafsl0wpMe.png

He has only +/-9V. He used an empty clip to hold the red of the left battery to the black of the right battery.
 
Back
Top