high stability bias circuit for photodiode

[deep78]

Hi,
I am working with a photodiode optimized to have a bandwith higer then
5 GHz on a 50 ohm load. 1dB saturation current is arond 40mA.
The best bias circuit for such a kind of diode would be a low noise DC
voltage source that can keep the voltage fixed at 9V -10V even if
current is varying from 0 to 40mA in 50ps-100ps.
What would you suggest to design such a DC source ?

 

[John Larkin]

Hi,
I am working with a photodiode optimized to have a bandwith higer then
5 GHz on a 50 ohm load. 1dB saturation current is arond 40mA.
The best bias circuit for such a kind of diode would be a low noise DC
voltage source that can keep the voltage fixed at 9V -10V even if
current is varying from 0 to 40mA in 50ps-100ps.
What would you suggest to design such a DC source ?

How about a 10 volt linear regulator with some bypass caps on the
output?

John

 

[Kevin White]

Hi,
I am working with a photodiode optimized to have a bandwith higer then
5 GHz on a 50 ohm load. 1dB saturation current is arond 40mA.
The best bias circuit for such a kind of diode would be a low noise DC
voltage source that can keep the voltage fixed at 9V -10V even if
current is varying from 0 to 40mA in 50ps-100ps.
What would you suggest to design such a DC source ?

Are you sure you need 40mA? You may be making your task more difficult
than it need be.

I would expect a InGaAs diode with 1dBm input to have a photo-current
of about 1mA. An avalanche diode would have a higher photo-current but
it would need a higher voltage and you wouldn't need to use one with
1dBm of input available.

kevin

 

[[email protected]]

Hi,
I am working with a photodiode optimized to have a bandwith higer then
5 GHz on a 50 ohm load. 1dB saturation current is arond 40mA.
The best bias circuit for such a kind of diode would be a low noise DC
voltage source that can keep the voltage fixed at 9V -10V even if
current is varying from 0 to 40mA in 50ps-100ps.
What would you suggest to design such a DC source ?

In the good old days, a mercury battery (or a string of them) was/were
the bias supply of choice for stability and low noise. Even today, no
solid-state supply can match a battery for low noise characteristics. Plus, a
battery can be floated with gigohms of isolation.

Jim