Electronics > Projects, Designs, and Technical Stuff
Generating Biphasic Signal with OpAamp
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A.Ersoz:
But I measure many times that the OpAmp gets -5V and 5V. The interesting point is that two days ago the same circuit works properly. 
capt bullshot:
No idea anymore.
Just double check all your components and signals.
A.Ersoz:
Thank you!
A.Ersoz:
I fixed the problem with connecting the -5V power with a jumping cable. Because one of the IC doesn't have -5V power.

I have one more question.

When I measure signal after a resistor (R1=25k in TINA TI design) which at inverting input of the opamp, I get this signal which is attached to this post. But when I measure from another howland pump configuration, I didn't get same signal at same node. The measured signal is just zero. Why is that happen?

A.Ersoz:
I have just solved the problem couple of minutes ago.

I check one by one each of the component with a SMD tester (http://www.mastech-group.com/products.php?cate=104&PNo=76). I realized that R2 resistor value supposed to 34k but I measured 20 Ohms. So I removed the component and check the its pads. I found that there had been a short circuit between of them. When I double check the layout, GND connection makes a short circuit a trace which is connecting R2 to noninverting input of the OpAmp. Hence, I broke the trace and solder a jumping cable according schematic design.

Actually I did this design with Altium. I run design rule check before the fabrication and the program didn't report any short circuit.

Anyway, the problem and its solution is for your information.
 
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