I am trying to breadboard a simple circuit that uses a piezoelectric transducer with an amplifier IC powered by a 5 volt DC powersupply. It all seems straightforward but it requires 5 v to the Ic amp which I have done. Then it needs a variable voltage -1 to -5 volts to the piezoelectric sensor. I am using a voltage divider (variable pot) from the same powersupply to create the range of voltages. It works great but only puts out positive voltages even when I reverse the + and - to the pot. How can I get -1 to -5 volts? Looks like I need a second powersupply? Thanks for the help!