Check out this groovy circuit I came up with!

0->3.3V PWM (20-80% duty cycle) 
                V+
                ^
                |
                \
             R1 /
                \
                |
                +--|>|----.
                |         |
                |       __|__|
                |      | / \   3.3V
                |       /___\  Zener
                |         |
0->3.3V >---||--+--|<|----+----->  >----.
                |         |             |
                \        ===            \ Amp
             R2 /         |             / Input
                \         V             \ ~30k
                |        GND            |
                V                       V
               GND                     GND