I searched around but was not able to find what i was looking for. Maybe that is because what i want to do is not the right method?

I am open to suggestions as well. I am just stuck.

This is what i have so far but i cannot control the negative side correctly. The top (positive) works but the negative side seems to need negative voltage.

I am trying to have a lower chip count so i don't want to use an op amp if possible.

Thank you for any insight you could lend me.

The bottom is not completed and i left off the buck to the right of the circuit because i cannot even get the correct voltage to it.

I was attempting something similar to the top on the bottom without luck.
Thanks =)

 

The bottom should give you a half-wave negative rectified voltage. Don't know why it doesn't.

Note that you need resistors in the collector and base of Q2 or you will zap Q2 and/or Q1.

 

Yes there are current limiting resistors up top now =) I poped one by accident the first time through.

The bottom works and gives me -20V but the problem is i cannot control any transistors as all the base voltages are negative and i need to be able to control with 0-5V not negative voltage.

Thanks

 

You can control a negative voltage with a positive voltage by using a grounded base PNP transistor. The control voltage goes through a resistor to the emitter and the collector goes to the negative voltage load. Note that the control voltage emitter current approximately equals the collector current for a grounded base configuration.

 

I totally forgot about that!

I learned about it but never applied it before thanks for the help i spiced it and it worked so i will try it a little later today.

Thank you for the help.