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  • TI Thinks Resolved

nano amps to several amps VCSEL driver circuit

Hi,

I'm a graduate student in optical sciences. I encounter some problems in designing a VCSEL driver circuit. 

We need to design a VCSEL driver circuit to drive and modulate a VCSEL by the current. Modulation requirements are as follow:

1. Pulse current of which peak value is around 45 amps

2. Pulse train reptition rate is 1kHZ

3. Pulse duration is around 1 nanosecond. Duty cycle is super small 1ns/1ms. Rise and fall time is 1ns respectively.


We have a 10nA-1000nA (100 levels, 10nA step) current source right now. It can meet the requirements 2 and 3. But the amplitude is ultra low. 

So I was wondering if I can have a suitable amplifier to amplify this nano-amp to 45 amps? The difficulty is although the duty cycle is super small, the rise and fall time of each pulse is nanosecond scale. The amplifier should be fast enough. Also, our input current should be adjustable. For example, 10nA corresponds to 45A, 20nA corresponds to 46A, 30nA corresponds to 47A, etc.

  • Hi Sifang,

    Thanks for the post, and sorry for the delay in response. We are still catching up from the recent holiday season. We will aim to have a response to you by the end of this week (1/5).

    Thanks,

    Michael
  • Hi Sifang,

    Thank you for reaching out to TI. I am not sure if we have a suitable amplifier / driver. Have you looked on TI.com at the datasheets of our 10G VCSEL drivers ONET8501V, ONET1191V ? To answer the duty cycle / sensitivity questions, I will need to ask our optical expert, back on Jan 15th.

    Regards
    David
  • Hi Sifang,

    All our VCSEL drivers can only drive output currents of up to tens of mA. We do not have amplifier/driver components for driving such high currents to a laser. To my knowledge, none of the standard VCSEL diodes operate at such high bias/modulation currents.

    Also, our VCSEL drivers have been designed mainly for the high-speed communication applications (> 4 Gbps datarates), so the LCF of the internal circuitry is typically much higher than KHz range.

    Thanks,
    Sri

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