Chopped laser driver for low noise applications

A laser diode circuit (10, 12), comprising:

• (a) a laser diode (12);
• (b) a laser driving current source (16);
• (c) an oscillator means (20, 22) including a ring oscillator having a first inverter provided with hysteresis to cause a second inverter to have different slew rates for high to low transition and low to high transition;
• and
• (d) a current steering means (18) coupled to said laser driving current source (16), said oscillator means (20, 22), and said laser diode (12) for alternately coupling said laser driving current source (16) to the anode (12a) and the cathode (12b) of the laser diode (12) in response to said oscillator means (20, 22).

A circuit (10) for driving a laser diode (12), comprising:

• (a) a programmable current source (16);
• (b) a ring oscillator (22) generating a first frequency, the ring oscillator having a first inverter provided with hysteresis to cause a second inverter to have different slew rates for high to low transition and low to high transition, said ring oscillator having an output (22f);
• (c) a phase splitter (20) having an input (22c) and first (22a) and second (22b) outputs, said first and second outputs (22a, 22b) being substantially 180 degrees out of phase with each other, said input (20c) being coupled to said output (22f) of said ring oscillator (22);
• and
• (d) a differential output driver (18) coupled to said programmable current source (16) and said phase splitter (20) for alternately coupling said programmable current source (16) to the anode (12a) and the cathode (12b) of laser diode (12) in response to said oscillator means (20, 22).