Switch Vcc to Ground with a control bit
In general, CMOS inverters won't be able to source 3A. As Wouter van Oeijen stated, an H-Bridge is what you want. The princicple of operation is shown below. As shown, S_B1 and S_B2 are closed, causing a current flow from right to left. When you instead close the A-Switches, the current is reversed. When you want no current at all, open all switches. In reallity, the switches will of course be transistors requiring a decent driver stage.







simulate this circuit &ndash; Schematic created using CircuitLab

A problem with these bridges is, that you must not close i.e. A1 and B1 at the same time. Therefore a certain delay has to added when reversing the current.

What exactly is your load, are you sure that you can assume an ohmic load? Or is it a motor?