high stability bias circuit for photodiode

Nov 20, 2005 3 Replies

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deep78 20 years ago

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 ?

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John Larkin 20 years ago

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

John

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Kevin White 20 years ago

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

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jmeyer 20 years ago

On 20 Nov 2005 11:52:20 -0800, "deep78" wroth:

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

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