Comparator in spice help.

Hello, i am hoping someone can help me with LTspice. I can't seam to get comparators to work. I don't know if it is me or spice that is failing.

The comparator is only outputting 700mV while on. It is being supplied 20 volts and should be outputting 20 volts?

Nope, it's working correctly. You are simply allowing the negative power supply to pull up to where the output is only 0.7V.

Try tying your negative comparator supply input to ground instead. It'll work better.

Ahh yes i see. Thanks for the help with that.

I have run into another similar problem. The bottom comparator in this file works good. The top is wired the same as the bottom comparator however it has a totally different output relative to the negative supply. I don't think it is the same problem as last time since the supply is steady. It works even worse with a single supply driving both comparators.

I can't see what is going on, any help would be much appreciated

masteropie said:

I have run into another similar problem. The bottom comparator in this file works good. The top is wired the same as the bottom comparator however it has a totally different output relative to the negative supply. I don't think it is the same problem as last time since the supply is steady. It works even worse with a single supply driving both comparators.

Click to expand...

The top transistor has the negative supply at its collector instead of the positive supply.

Whoops, your right. Still have the same problem though. The top comparator is oscillating as well as only outputting under a volt. I guess this is caused by positive feedback?