Hi
i establish a circuit in laab
an opam amplifier with symmetric voltage . In input of the circuit theere a small signal form a generator



When i trying to meausre the output voltage i see that one suplly voltage the value decrease
why ?




thank
George

 

I am going to rephrase what I think you are asking.

When you try to measure the voltage at the output pin of the opamp, the voltage of one of the power supplies drops.

Is that correct?

 

What power supply are you using?
Does it have a constant current adjustment?

 

What point in the circuit are you using as the reference for the voltage measurement??

 

Which supply? V+ or V-
WHen does it decrease and how much?

 

hi
i want to measure the outtput voltage at pin 6
in figure show that connect the - output to + output of power supply this is the reference for all measure

 

The reference is ground.

 

Can you please draw the connections when measuring the pin 6 output ?
Are you measuring between pin 6 and the Ground ?
I think you are, by mistake, measuring voltage between pin 6 and power supply + and power supply - .
Or how will you know that power supply voltage Drops?

 

Can you please draw the connections when measuring the pin 6 output ?
Are you measuring between pin 6 and the Ground ?
I think you are, by mistake, measuring voltage between pin 6 and power supply + and power supply - .
Or how will you know that power supply voltage Drops?

the ground for my circuit is the common connection of - and + this ground IS WRONG ?

 

the ground for my circuit is the common connection of - and + this ground IS WRONG ?

It is correct, and often called the "common" , which is more correct than calling it "Ground". The reason I say that is because ground is also a connection to the common side of everything else. Common is the reference point within a circuit or system, and so it is only a part of that system until it is connected to something else. That can be a great benefit for analysis because it is not connected to unknown quantities.

 

It is correct, and often called the "common" , which is more correct than calling it "Ground". The reason I say that is because ground is also a connection to the common side of everything else. Common is the reference point within a circuit or system, and so it is only a part of that system until it is connected to something else. That can be a great benefit for analysis because it is not connected to unknown quantities.

I use a signal generator in input pin 2 and an oscilloscope in pin 6 and the power supply for symmetric dc voltage where is the problem ?

 

Both the signal generator and the oscilloscope also have the second connection, which would be to the common. Every voltage measurement is between two points. Mostly that second point is the "common" of the circuit. But not always, THAT can lead to confusion.

It is a lot like measuring distance, which is always between two points.

 

Tell us EXACTLY how everything is connected, including ground on your two power supplies and the ground clip in your oscilloscope probe. I suspect you are shorting one of the power supplies with your oscilloscope ground.

Edit: also the signal generator ground.

 

Tell us EXACTLY how everything is connected, including ground on your two power supplies and the ground clip in your oscilloscope probe. I suspect you are shorting one of the power supplies with your oscilloscope ground.

Edit: also the signal generator ground.

In the common ground of circuit ( define by the connection + and - in power supply ) connected all the other ground from the generator and the oscilloscope

 

What is the current setting on the power supplies?
Show us a photo of the PSU.

 

I use a signal generator in input pin 2

What model signal generator? Might need a capacitor in series with R1.

 

I see a language and meanings problem here, as well as a desperate searching for what the problem actually is. That is to say that there is something important that we do not know just yet, And I am not sure what that missing bit is.
The first circuit in post #1 is not actual, the second circuit in post #1 includes neither power supply connections nor any hint as to te amplitudes of the signals, nor DC offsets.
ALL OF THE VOLTAGE MEASUREMENTS ARE NEEDED FOR A MEANINGFUL EVALUATION.

 

I see a language and meanings problem here, as well as a desperate searching for what the problem actually is. That is to say that there is something important that we do not know just yet, And I am not sure what that missing bit is.
The first circuit in post #1 is not actual, the second circuit in post #1 includes neither power supply connections nor any hint as to te amplitudes of the signals, nor DC offsets.
ALL OF THE VOLTAGE MEASUREMENTS ARE NEEDED FOR A MEANINGFUL EVALUATION.

a complete circuit

 

This is what I asked in Post #8
This drawing is for Output Signal Measurement. It is correct.
What is the Drawing when measuring the Supply Voltage?

 

Hi George. Your power supplies need to be "floating" to be connected in series. If their negative terminal is connected to Chassis, one of them may be shorted (the bottom one). Your scope definitely has ground clip connected to Chassis, so when you connect it between your power supplies (Ground point of your schematic) it also may interfere with the operation of the bottom power supply