HF LED Drivers

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HF LED Drivers

• M. Miller
• Y. Onel

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HF LED Drivers

• The HF pulser outputs an optical pulse of
  approximately 25 nsec from a blue (Nichia
  NSPB500S) LED
• The anode of the LED is biased at 5.5 VDC. This
  voltage is variable from 5.5 VDC to 2.5 VDC.
  This permits intensity variation of the optical
  output
• The cathode of the LED is biased at 5.5 VDC. A
  pulse from 5.5 volts to 0 VDC causes the LED to
  be forward biased. The pulse has a width of
  approximately 12 nanoseconds at 0 VDC. The
  cathode voltage is raised to 11 VDC for
  approximately 500 nanoseconds to remove carriers
  from the LED. This helps to eliminate the tail
  of the optical output.

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HF LED Drivers

• The prototype pulser has two inputs. One input
  will generate a 25 nanosecond optical pulse,
  regardless of the duration of the electrical
  input. The second input generates an optical
  pulse that is equal to the electrical input pulse
  plus 10 nanoseconds.
• The prototype pulser uses an isolated BNC output
  connector. The shield of this BNC is at a
  potential of 5.5 volts and cannot be connected to
  ground.
• The prototype is powered with 15 VDC. Two on
  board regulators reduce the voltage to 11 VDC
  and 5.5 VDC. In operation, the regulators
  generate heat and feel warm to the touch. This
  is normal operation.

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HF LED Drivers
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Electrical Output Pulse
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Optical Output Pulse