Cheapest way to microvolt measurements

[2N3055]

First thing you had to check whether Hamamatsu has any application notes for what you need.

At link
https://www.hamamatsu.com/resources/pdf/ssd/si_pd_circuit_e.pdf
there is, among other stuff, two circuits for exactly your diode. They also give general layout advice. That should be more than enough to get you started.

As far as other circuit, it's like Kleinstein said..

I'm looking at signals (with an oscilloscope) with very fast edges. From what I know (and I may be wrong in this) there's no way to build a transimpedance amplifier that fast. In the application note that you linked they talk about 100MHz BW max which really is not enough.



Here's why the 50 Ohm.

One of the amps is not TIA there. It's basically what you doing, a diode terminated with resistor and amplified.
By using amp, you can also play with optimal diode termination resistor, to maximize voltage and not lose much speed.
By using faster amp and lot of care doing layout, you can get to few hundred MHz bandwidth with 10x amplification without resorting to anything esoteric...That should be enough.

[dietert1]

Some years ago we got an old HP 81519A Optical Receiver 400 MHz. Not really a precision device but turned out to be very useful. We successfully adapted it to a contemporary SMA type fiber interface. The service manual shows an example circuit. There was an intro in the HP Journal January 1985, p27.

Of course, if the photo diode is external, a 50 Ohm interface is natural.

Regards, Dieter

[MegaVolt]

I did not quite understand the required frequency. But for example AD8015 ... more than 100 MHz.