New to circuits, and been trying to get various op amps to work they all fail.

On a split rail supply connecting +12 & -12 volt, where does the virtual earth connect to, there plenty of circuits to view but the earth symbol is shown but where is this connected to in the circuit.

Thanks

 

The virtual ground is called common or COM. This is the 0V reference in your circuit. The symbol sometimes used to represent COM is an inverted triangle.

Any part of the circuit that needs to be referenced to 0V is connected to COM.

It is not always necessary to connect this to earth ground.

 

The op amp output is referenced to the the common (0v) of the +12v -0v- -12v supply.
Max.

 

Thanks, So on the split rail I have the +12 & Zero/common & -12 and the zero is the virtual earth.

 

Thanks, So on the split rail I have the +12 & Zero/common & -12 and the zero is the virtual earth.

Yes, correct.
Max.

 

Can you explain why this does not work .3 volts in to amplify to 1.5 volts

 

http://www.talkingelectronics.com/projects/OP-AMP/OP-AMP-1.html
Max.

 

Interchange the inverting and non-inverting inputs of the opamp.

 

AND, connect the node that is (the low side of the battery connected to the 2K resistor) to the center point of the +/- power supplies. We call this node Ground (GND).

ak

 

Thanks is this correct, i'll try it now
Paul

 

What ever the long device is on your output, should also be connected to GND.

 

The ground should go to the non-inverting (+) input. The 1k is the input and should not be grounded.

 

I have a PWM signal passing through a RC low pass filter, The output from the filter is a small sawtooth waveform and I get .9 volts and 1.6 volts variation when I use a PWM transmitter as seen on the scope.
How do I turn the small .9 volt 1.6 volt range to +/- 10 volt. If I put it through a second op amp the PWM waveform comes back in. Looking for a clean +/- 10 volt.

Thanks Paul