choice of photodiode amplifier

A

acburiti

New Member

• Dec 22, 2008

• #1

Hi,

can somebody show me a good photodiode amplifier using opamp? there are a lot of them available, but I don´t know the better one.

any kind of help will be very welcome.



antonio

 

H

Hayato

Member

• Dec 22, 2008

• #2

What is the application?

I think the best thing is to use an phototransistor.

 

A

acburiti

New Member

• Dec 22, 2008

• #3

thanks for the info.

i'll use a photodiode to acquire signals from a modulated infrared LED, and then using a bandpass filter to get the main frequency (fundamental).

would you have some tip?

 

H

Hayato

Member

• Dec 22, 2008

• #4

Right.
You'll be working with analog modulation? Because if it is pulsed, it is much more simplier.

 

audioguru

Well-Known Member

Most Helpful Member

• Dec 22, 2008

• #5

Use an IR receiver IC that has a visible light filter, a photo-diode, a high gain amplifier with AGC, a bandpass filter and a demodulator.

 

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eblc1388

Active Member

• Dec 23, 2008

• #6

acburiti said:

can somebody show me a good photodiode amplifier using opamp? there are a lot of them available, but I don´t know the better one.

Click to expand...

You might want to watch this video on how to use and select amplifier for photodiodes.

It is presented by Paul Rako of National Semiconductor.

**broken link removed**

 

A

acburiti

New Member

• Dec 23, 2008

• #7

Hayato,

the modulation is pulsed (~ 10kHz), 25% duty cycle.

 

H

Hayato

Member

• Dec 23, 2008

• #8

Audioguru's tip is very good.

I'd prefer to use a phototransistor, since it's pulsed.

But if you really want to use a photodiode, it's better to "buffer" it.

Use a FET input OPAMP, like TL082 or TL072, to build the buffer circuit. Since we can consider a photodiode as a very high impedance source, if you use a BJT input opamp, the voltage will be (not always) unpredictable (it will be more difficult to find "trigger voltage" for the opamp).

Then do as Audioguru says. Don't forget the visible light masked photodiode, it's very important.

 

audioguru

Well-Known Member

Most Helpful Member

• Dec 23, 2008

• #9

IR receiver ICs work at frequencies of 30kHz and higher, not as low as 10kHz.

 

H

Hayato

Member

• Dec 23, 2008

• #10

audioguru said:

IR receiver ICs work at frequencies of 30kHz and higher, not as low as 10kHz.

Click to expand...

Yes.
Some days ago I was trying to use a IR receiver set, from a Sharp VCR, it was not working... Then, I looked into a datashee... There was a high-pass filter there.