Sagging square wave output from non-inverting opamp

[level6]

I'm working on a device that generates low frequency triangle and square waves. The final output is amplified by a non-inverting opamp circuit with a gain of about 5. The problem I'm having is the square wave output is not symmetrical, it sags toward zero at both the positive and negative pole. The input into the opamp looks fine, as illustrated by the screen capture from my scope. Yellow is the output, blue the input into the output circuit.

What would be causing this and how can I remedy it? BTW the triangle output is fine.

Schematic of output circuit attached.

[David Hess]

The input does not look square to me.  The gain multiplies the amplitude but also the slope.

[level6]

The input does not look square to me.  The gain multiplies the amplitude but also the slope.

You're right. I went back and zoomed in on the input and see that it is just reliably amplifying the input. The input is coming off a voltage divider. That may have something to do with it. More research...

[StillTrying]

Is the square wave shape good when it's not connected to the 100k, just as a check of the square and scope.

Are the +/- supplies to the TL074 good.

[level6]

Is the square wave shape good when it's not connected to the 100k, just as a check of the square and scope.

Are the +/- supplies to the TL074 good.

Power supply is fine, it's from my bench supply. I'm going to look into eliminating interaction with other parts and see if that changes thing for the better.

[Ash]

Does the output jack _really_ short the output to ground when no plug is connected as shown on the schematic? That's probably not a good idea either...

Ash.

[level6]

Does the output jack _really_ short the output to ground when no plug is connected as shown on the schematic? That's probably not a good idea either...

Ash.

Woops! Thanks for pointing that out. Right now I'm working with a prototype on perfboard and I didn't implement that short. I will certainly change that in the design!

[Cerebus]

Given the thickness of those traces I suggest that you crank the oscilloscope timebase way up and see what's going on there. I would not be surprised to see that those thick traces are actually oscillation or ringing on the 100mV+ order of amplitude.