Discrete high-speed laser modulator schematic

[drlava]

This was an early modulatable laser driver that I designed for <300mA diodes. It is capable of very high speed modulation due to its discrete layout, peaking capacitors, and current shunt type modulation, but has drawbacks as a few resistors need to be re-tuned for every different diode type. The power supply needs to be of the regulated type. Also because it is purely a feed-forward design it is very stable with any load wire length/inductance. I don't use this much anymore, so thought I'd release it into the public domain.

If you are interested in PCBs I still have a few, also PCB layout images and Orcad design/simulation files.

D6,V4 are only there to simulate the load laser; R4, V1 and the clock source are for simulation purposes also.

[Nyla]

Thanks drlava! This is a great schematic.

I plan to use it for my 803t diodes, you mentioned some resistors need to be recalculated for use with different diodes. Which ones exactly?

Also, are there any common alternative for Q1 and Q2?

[drlava]

Thanks drlava! This is a great schematic.

I plan to use it for my 803t diodes, you mentioned some resistors need to be recalculated for use with different diodes. Which ones exactly?

Also, are there any common alternative for Q1 and Q2?

Hi, the resistors that need to be changed are:
R1 R6 R7 R3 R2 R14 R10
Any transistor could be used instead of the MPS3704 as long as it has appropriate current and power ratings and hFE gain similar.