Home Forums SPICE Converting mV to pulses in OptiSPICE 5.0

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• #79764
Sylwia Kojtek
Participant

Could it be possible to determine the optical power of the diode in pulses? Value or time waveform.

Best regards,
S.K.

• #80455

I assume by diode you mean photodiode and you want to control it’s output power using pulses (voltage). In this case yes you can using pulse width modulation (PWM).Photodiodes response is usually slow therefore it takes the average of the input train of pulses, if the pulses are short enough. For example, consider a train of pulses with (0 as GND) and (1 as 5V) and the pulse width is short enough. In this case, if the input sequence is (111111), then the output from the diode will be equivalent to (5V input “the average of the sequence”). And if the input sequence is 101010 which corresponds to (5V-0V-5V-0V-5V-0V), then the diode will average this sequence and give you an output corresponding to this ~2.5V. I hope this answers your question.

• #83059

I assume by diode you mean photodiode and you want to control it’s output power using pulses (voltage). In this case yes you can using pulse width modulation (PWM).Photodiodes response is usually slow therefore it takes the average of the input train of pulses, if the pulses are short enough. For example, consider a train of pulses with (0 as GND) and (1 as 5V) and the pulse width is short enough. In this case, if the input sequence is (111111), then the output from the diode will be equivalent to (5V input “the average of the sequence”). And if the input sequence is 101010 which corresponds to (5V-0V-5V-0V-5V-0V), then the diode will average this sequence and give you an output corresponding to this ~2.5V. I hope this answers your question.

• #80457
Sylwia Kojtek
Participant

Thank you,

Do you know how to plot the current-voltage characteristics of the laser diode shown in the attached figure in program OptiSPICE version 5.2?

• #83061
Sylwia Kojtek
Participant

Thank you,

Do you know how to plot the current-voltage characteristics of the laser diode shown in the attached figure in program OptiSPICE version 5.2?

• #80467

Hi,

Yes you can plot the I-V characteristics of the Laser. You should replace the pulse source with the DC source and sweep the DC voltage. Put a resistor in series to DC source and the Laser. Put one resistor with very high resistance (1000k Ohm) in parallel to the Laser. Put one probe to the Pin of the laser (direction of going into the laser) to measure the current going through laser as a function of swept vdc source. Put another probe to the wire connecting resistor to measure the voltage across (which is equal to the voltage across Laser).
The schematic of the testing circuit is attached along.

• #83071

Hi,

Yes you can plot the I-V characteristics of the Laser. You should replace the pulse source with the DC source and sweep the DC voltage. Put a resistor in series to DC source and the Laser. Put one resistor with very high resistance (1000k Ohm) in parallel to the Laser. Put one probe to the Pin of the laser (direction of going into the laser) to measure the current going through laser as a function of swept vdc source. Put another probe to the wire connecting resistor to measure the voltage across (which is equal to the voltage across Laser).
The schematic of the testing circuit is attached along.

• #80481
Sylwia Kojtek
Participant

Hi,
Thank you very much for your answer, the characteristics of the IV Laser are the same as those of its measurements.

Regards,
Sylwia Kojtek

• #83085
Sylwia Kojtek
Participant

Hi,
Thank you very much for your answer, the characteristics of the IV Laser are the same as those of its measurements.

Regards,
Sylwia Kojtek