Hi guys, I've made the schmitt trigger circuit 2/3 the way down this page -
http://www.swarthmore.edu/NatSci/echeeve1/Class/e72/E72L2/Lab2(OpAmp).html
When I tested this circuit with an LED everything seemed fine. I then inserted a transistor to the output stage which made the LED light continuously. I measured the voltage at the op amps output - the circuit was still working, but the 'low' voltage was about 1.5V! High is about 15V.
I switched back the LED and I observed the same thing, but the LED responded as if the low was 0V (completely turned off). Maybe to do with the op amps output current limitations? Anyway that isn't the issue here, I'm using this circuit to drive a relay so I need that transistor in the output stage. How can I make the op amps 'low' voltage 0V? I'm using a single rail power supply by the way.
Cheers guys!
http://www.swarthmore.edu/NatSci/echeeve1/Class/e72/E72L2/Lab2(OpAmp).html
When I tested this circuit with an LED everything seemed fine. I then inserted a transistor to the output stage which made the LED light continuously. I measured the voltage at the op amps output - the circuit was still working, but the 'low' voltage was about 1.5V! High is about 15V.
I switched back the LED and I observed the same thing, but the LED responded as if the low was 0V (completely turned off). Maybe to do with the op amps output current limitations? Anyway that isn't the issue here, I'm using this circuit to drive a relay so I need that transistor in the output stage. How can I make the op amps 'low' voltage 0V? I'm using a single rail power supply by the way.
Cheers guys!