Hi,

I am looking to design a analog laser driver to produce sine chirp exitation to a IR laser diode.
I need about 50-80 mA of modulation current and a bias of about 10-20 mA.

I new to analog design so if any of you have any experience your are willing to share, I will be greatfull.

Thx

Just to be clear the chirp waveform will be produced by a DAC.

 

Just to be clear the chirp waveform will be produced by a DAC.

You have a DAC that can generate a 200MHz chirp?
What is the DAC model number and what are you driving it with?

 

You have a DAC that can generate a 200MHz chirp?
What is the DAC model number and what are you driving it with?

I plan to use the DAC3151 a 500 MSPS 10 bit DAC and drive it with a FPGA.
Also if 200 Mhz chirp is to ambitous I could lower the chirp to 100 Mhz

 

I plan to use the DAC3151 a 500 MSPS 10 bit DAC and drive it with a FPGA.
Also if 200 Mhz chirp is to ambitous I could lower the chirp to 100 Mhz

A 200MHz chirp is way too ambitious for that DAC by several orders of magnitude.
A 10-bit DAC requires 1024 samples per one sinewave cycle, thus the maximum sinewave you can generate is 500MSPS/1024S = 488kHz.

For a 200MHz chirp sinewave you would need a DAC with a 205 GSPS data rate.
Don't think you can get that off-the-shelf.

 

A 200MHz chirp is way too ambitious for that DAC by several orders of magnitude.
A 10-bit DAC requires 1024 samples per one sinewave cycle, thus the maximum sinewave you can generate is 500MSPS/1024S = 488kHz.

For a 200MHz chirp sinewave you would need a DAC with a 205 GSPS data rate.
Don't think you can get that off-the-shelf.

I dont need a perfect sine wave at 200 Mhz, I dont get where you get the 1024 sample requirement. I just need a couple sample and a anti aliasing filter to get the desired output.

Lets assume I use a 400 Mhz bandwith function generator, do you have a idea how to design the laser driver ?

 

I dont get where you get the 1024 sample requirement

If you want to use the full 10-bits to generate a good sinewave than it requires 1024 (10-bit) samples per cycle of the sinewave.
You do know how a DAC works?

Lets assume I use a 400 Mhz bandwith function generator, do you have a idea how to design the laser driver ?

Depends upon the accuracy and distortion of the current waveform to the Laser you can tolerate.

 

If you want to use the full 10-bits to generate a good sinewave than it requires 1024 (10-bit) samples per cycle of the sinewave.
You do know how a DAC works?
Depends upon the accuracy and distortion of the current waveform to the Laser you can tolerate.

I do know how a DAC work and I have used plenty of time in the past with RF mixer.
But the question is how to design a laser driver with 200 Mhz bandwith.

 

I do know how a DAC work and I have used plenty of time in the past with RF mixer.

Well, from your question about why it took 1024 samples per cycle, I wasn't sure.

But the question is how to design a laser driver with 200 Mhz bandwith.

You need to answer my query in post #6 about required accuracy and distortion first.
The first rule in doing any design is nail down the requirements.

 

There are special microcircuits for laser drivers and a description of their internal structure. Take advantage of this for your circuit.

 

Well, from your question about why it took 1024 samples per cycle, I wasn't sure.
You need to answer my query in post #6 about required accuracy and distortion first.
The first rule in doing any design is nail down the requirements.

I need a flat amplitude responce to about 200 Mhz, the distortion is not critical. It for a CWFM lidar where I mix the modulated chirp with the echo from a object. In my simulation it even work with square wave but with added noise to the messurement.

To make it short lets say that a THD of 10-20% is acceptable