Here's an oscillogram of a high power Cree® XLamp® CMA3090, driven with 60A pulses.
Yeah, I studied it in the other thread! Real scope shots of linear
a few 1us light pulses for comparison are very rare, I only know of 1 other, other than yours and mine, some others are current waveforms or just sims.
I can't identify which PD your SFH2201 is, 4mA seems like a massive (not very linear) PD current, I'm usually only around 20-200uA.
Here's one of my basic
improvements to the "just PD and 50R" mostly to improve sensitivity.
* The impedance seen by the PD is <23R.
* The 510R gives X10 more signal than the PD + 50R.
* No feedback cap needed.
* The 15R makes it a 50R output. (I've not tried a 50R connection)
* Bandwidth -1@ ~50MHz and -3@ ~100MHz.
* The 0.65V emitter-collector is a bit low, and is a DC offset, but seems to work in practice.
* = in theory, and/or measured in sim, results in practice
may do vary.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
I've made the latest 2 TR version too small to add another stage to the 7660's -16V, I'll try inserting another -9V which would total -26V on the PD. The PD and 5k1 feedback R are already air connected to the RF TR's base, to save every 0.25pF.
Most of the time I don't know if the speed/edge limits are the PD, or the best that that LED can do.