PWM circuit dimming a negative load bulb

Hi Guys.
I have a pwm controlled tip31C dimming circuit like this.
It works great.

pwm

But I need to do the same transistor loaded lamp on -12V rail.
Please could anyone help me ? I have some tip32C here.

Thank you.

It is not clear what you mean by "same transistor loaded lamp on -12V rail".

There are two basic types of transistor switches: high side and low side. Typical wiring with bipolar transistors is shown below. Either can be used with PWM brightness control.

Hi J remington.
I´ve found this and works with -12V with some mods.
Thank you!!!