Photodiode falltime problem

[pooya_BA]

Hello
I have a problem with the photodiode. I bought the SFH 2704 photodiode and connected it directly to the oscilloscope circuit without an electronic circuit.
The fall time of this very, very long piece was about 380 microseconds, while in the information of this piece, the fall time was 67 nanoseconds.
What do you think is the problem? And how can I solve this problem?

The diagram below shows the output of the photodiode with a pulse of 160 microseconds.
This pulse is taken with a commercial PDA10A2 photodiode and is exactly equal to the pulse, meaning that the light source does not have a short time.

 

[Pommie]

Oscilloscope capacitance?

Mike.

 

[pooya_BA]

Oscilloscope capacitance?

Mike.

1 MΩ in parallel with 13 pF

 

[Pommie]

I wondered as you said "Oscilloscope circuit" so wondered what the circuit was. The datasheet states a fall time of 67nS which suggests something else causing the slow response. Think I'd try buffering it to see what happens.

Mike.

 

[pooya_BA]

I wondered as you said "Oscilloscope circuit" so wondered what the circuit was. The datasheet states a fall time of 67nS which suggests something else causing the slow response. Think I'd try buffering it to see what happens.

Mike.

No, I mean there is no circuit to amplify the photodiode and I connected the photodiode directly to the oscilloscope.

 

[dougy83]

Put a resistor across the photodiode to speed it up.

 

[kubeek]

You need to use it reverse biased, normal photovoltaic operation is much slower.

 

[pooya_BA]

Put a resistor across the photodiode to speed it up.

Hello
I placed a 330 ohm resistor parallel to the photodiode.
falltime decreased but still a long time.
What else should I do?

 

[Xav]

Hello.

I Don't understand when you say " you connected it directly to the oscilloscope circuit without an electronic circuit ".

In the datasheet, the photodiode is polarised with 5V across a resistor of 50 Ohms.

 

[ChrisP58]

Hello
I placed a 330 ohm resistor parallel to the photodiode.
falltime decreased but still a long time.
What else should I do?

Performance specifications are dependent on certain conditions, and it's important that you match the conditions to achieve the same results.

Page 3 of the data sheet states that the conditions for rise and fall times are with a 50 Ohm load. That load resistor will be in parallel with the scope, not the photodiode.

 

[Xav]

The datasheet is not clear as almost always with Osram !
When I choose a device and before buy it, I always look before the datasheet to understand how to use it, especially schematics and conditions of test !