Hi all!
I am trying to test some simple op amp circuits before I ask my instrumental analysis students to build them in class and I am a little out of my depth. I took a fairly extensive analog electronics course in undergrad, but that was more than 10 years ago and I am a little rusty. My first attempt here was with a straightforward level detector and the output does not seem to be amplified, or in fact influenced by the power supplies in any way. Let me summarize what I've got:
1. None of our power supplies have negative voltage so I got some LT1054s to make a voltage inverter. That worked on the first try (woohoo!) and now I have reliable +/- power for the op amp.
2. I am using LM741 op amps, a function generator, and an oscilloscope. I am confident that my signals into the inverting and noninverting inputs are what I think they are. I set up a diode to check the signal in from the function generator and I'm just comparing to ground.
There is not much to this circuit so I am at a loss for troubleshooting. When I monitor the output of the chip given the input of a square wave from the function generator when the chip is not powered, I get a spike on the leading edge of each pulse, but it is not Vsat and it is short-lived. Then when I turn on the power supply, there is some mess that eventually dies down to what I have without the power on. Changing the magnitude of the rails has no effect on the output. This is best case scenario, worst case scenario I start to smell burning chip and then there is no output at all. I've probably fried 6-7 chips now. The current from the power supply is less than 0.05 A, and I've tried a variety of voltage magnitudes for the square wave (also tried sin wave).
Help!
I am trying to test some simple op amp circuits before I ask my instrumental analysis students to build them in class and I am a little out of my depth. I took a fairly extensive analog electronics course in undergrad, but that was more than 10 years ago and I am a little rusty. My first attempt here was with a straightforward level detector and the output does not seem to be amplified, or in fact influenced by the power supplies in any way. Let me summarize what I've got:
1. None of our power supplies have negative voltage so I got some LT1054s to make a voltage inverter. That worked on the first try (woohoo!) and now I have reliable +/- power for the op amp.
2. I am using LM741 op amps, a function generator, and an oscilloscope. I am confident that my signals into the inverting and noninverting inputs are what I think they are. I set up a diode to check the signal in from the function generator and I'm just comparing to ground.
There is not much to this circuit so I am at a loss for troubleshooting. When I monitor the output of the chip given the input of a square wave from the function generator when the chip is not powered, I get a spike on the leading edge of each pulse, but it is not Vsat and it is short-lived. Then when I turn on the power supply, there is some mess that eventually dies down to what I have without the power on. Changing the magnitude of the rails has no effect on the output. This is best case scenario, worst case scenario I start to smell burning chip and then there is no output at all. I've probably fried 6-7 chips now. The current from the power supply is less than 0.05 A, and I've tried a variety of voltage magnitudes for the square wave (also tried sin wave).
Help!