Hi all,
I am struggling to understand if my current source circuit is working correctly. I'm not sure if I'm placing my oscilloscope probes in the correct places either. Here are some pics to illustrate what I'm talking about.
This is my current source circuit. The bottom goes to GND even if I didn't draw it perfectly. I am sending a 100kHz square wave from an arduino into the op-amp. The op-amp is connected to the gate of the MOSFET. I was hoping the circuit would create a 5V square wave through the MOSFET but I'm not sure of this when I look at my scope.
Here is the scope screen when it is connected to the arduino only. GND of the probe to GND. Positive probe to the pin outputting the square wave. This would be point A (highlighted in pink) except that it is NOT connected to the op-amp yet. The square wave is obviously very clean and looks as it should.
Now I connect the arduino into my circuit (point B in pink highlight) and the wave looks similar just a bit less voltage and the edges are a bit rounded. So far so good..
Now this is where I get confused. I connect the scope probe to the output of the op-amp (point C in pink) and I get this:
No settings have been changed on the scope. The scope has been set to DC with 1V/div.
Why is the voltage reduced so greatly? It's no longer a square wave - can anyone explain why?
Is this even a decent circuit to create a 100kHz square wave? (BTW I was using the MOSFET because I may run the circuit with less resistance and draw up to 1000mA even though I am currently drawing ~25mA)
Any help or general comments are highly appreciated!
I am struggling to understand if my current source circuit is working correctly. I'm not sure if I'm placing my oscilloscope probes in the correct places either. Here are some pics to illustrate what I'm talking about.
This is my current source circuit. The bottom goes to GND even if I didn't draw it perfectly. I am sending a 100kHz square wave from an arduino into the op-amp. The op-amp is connected to the gate of the MOSFET. I was hoping the circuit would create a 5V square wave through the MOSFET but I'm not sure of this when I look at my scope.
Here is the scope screen when it is connected to the arduino only. GND of the probe to GND. Positive probe to the pin outputting the square wave. This would be point A (highlighted in pink) except that it is NOT connected to the op-amp yet. The square wave is obviously very clean and looks as it should.
Now I connect the arduino into my circuit (point B in pink highlight) and the wave looks similar just a bit less voltage and the edges are a bit rounded. So far so good..
Now this is where I get confused. I connect the scope probe to the output of the op-amp (point C in pink) and I get this:
No settings have been changed on the scope. The scope has been set to DC with 1V/div.
Why is the voltage reduced so greatly? It's no longer a square wave - can anyone explain why?
Is this even a decent circuit to create a 100kHz square wave? (BTW I was using the MOSFET because I may run the circuit with less resistance and draw up to 1000mA even though I am currently drawing ~25mA)
Any help or general comments are highly appreciated!