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Author Topic: Looking for low power TIA  (Read 1299 times)
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mare69
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« on: September 25, 2012, 09:44:32 21:44 »

I am looking for low power (Iq<100uA) transimpedance amplifier with low offset drift for "near DC" operation up to several kHz. It will be used in photodiode circuit operating in PV mode. So far what I found was for fast communications applications with supply currents above mA(-mps).

Any suggestions?
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motox
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« Reply #1 on: September 25, 2012, 11:52:04 23:52 »

Do you want to measure the optical power or receive data?

Check the following opamps: MAX406, MCP6031, MCP6041, OPA333-Q1
« Last Edit: September 26, 2012, 12:19:37 00:19 by motox » Logged
solutions
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« Reply #2 on: September 26, 2012, 01:06:29 01:06 »

Yes - what is it for? Can you use a ROSA?
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Gallymimu
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« Reply #3 on: September 26, 2012, 07:31:17 19:31 »

How much gain do you need?  That's an important consideration for choosing the amplifier.
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solutions
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« Reply #4 on: September 26, 2012, 09:53:46 21:53 »

FYI, a little backgrounder:

Gain - Vo/Vi or Io/Ii

A TIA performs an Ii to Vo conversion and its AMPLIFICATION is an IMPEDANCE TRANSformation (Vo/Ii), "trans" "impedance" "amplifier", not the unitless qty "gain", and is measured in ohms or dBohms.
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Gallymimu
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« Reply #5 on: September 26, 2012, 10:17:10 22:17 »

FYI, a little backgrounder:

Gain - Vo/Vi or Io/Ii

A TIA performs an Ii to Vo conversion and its AMPLIFICATION is an IMPEDANCE TRANSformation (Vo/Ii), "trans" "impedance" "amplifier", not the unitless qty "gain", and is measured in ohms or dBohms.

Gain is still relevant and as you stated in this case is V/A.  Gain bandwidth of the amplifier still has an impact on the design which is why I asked.  Sure if you want to get into the semantics in the strictest sense you are of course right.

Here is a nice article in EE Times on the topic.  The portions I am talking about related to the importance of the gain bandwidth of the opamp are in the later 3rd of the article:
http://www.eetimes.com/design/analog-design/4009969/Understand-and-apply-the-transimpedance-amplifier-Part-1-of-2-

Also note this follow on article:
http://www.eetimes.com/design/analog-design/4009969/Understand-and-apply-the-transimpedance-amplifier-Part-1-of-2-

OMG They use the word gain when talking about a TIA. They must be total hacks.  Smiley Just giving you a hard time.  I know you are here to help and educate.
« Last Edit: September 26, 2012, 10:33:40 22:33 by Gallymimu » Logged
Gallymimu
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« Reply #6 on: September 26, 2012, 11:26:43 23:26 »

Another great resource in this are, almost a "bible" is Photodiode Amplifiers: OP AMP Solutions by Jerald Graeme.  Though I think most of what the book has to offer is available on the net and in app notes.  It is nice to have all of the analysis and methods in one place.  There are PDF versions out there but I don't have one handy.
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motox
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« Reply #7 on: September 26, 2012, 11:54:40 23:54 »

There are PDF versions out there but I don't have one handy.
It will be very interesting to have such book. I can't find it... If someone has it, please be kind to share
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Magnox
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« Reply #8 on: September 27, 2012, 12:37:12 00:37 »

Ask, and ye shall receive (sometimes)

http://www.sonsivri.to/forum/index.php?topic=34999.0

Go to the last post for a working link.
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Gallymimu
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« Reply #9 on: September 27, 2012, 12:54:53 00:54 »

Yes - what is it for? Can you use a ROSA?

What is ROSA?  I'm sure it's something obvious but it isn't coming to mind!
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dotm
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C15H15NO2S


« Reply #10 on: September 27, 2012, 03:14:27 03:14 »

What is ROSA?  I'm sure it's something obvious but it isn't coming to mind!

it's a photoreceiver (photodiode and low noise tia)
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solutions
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« Reply #11 on: September 27, 2012, 05:55:16 05:55 »

Sorry

ROSA = Receive Optical Sub Assembly

Her brother is TOSA - Transmit Optical Sub Assembly
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mare69
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« Reply #12 on: September 27, 2012, 06:51:24 18:51 »

Thanks to all for good suggestions. MAX chips looks fine and pdf "Photodiode Amplifiers" was helpful.

Application is "detect whatever possible" with white LED and large photodide, measuring reflected radiation. Some materials have strange absorbtion behaviour.

M.
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solutions
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« Reply #13 on: September 28, 2012, 02:18:39 02:18 »

I think you're going to get in trouble with the white LED, unless you want to detect strong UV. It's laced with color shifting phosphors between the semiconductor and your light source.

If you want sensitivity, look up "APD", aka "avalanche photo diode" - however, they are usually reverse biased around 40+ volts
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« Reply #14 on: November 27, 2012, 06:25:18 18:25 »

If you're looking for a very wide temperature range, check out the LTC1053 from Linear Technology as well. I've used it with a 100K amplification (thanks for the terminology correction solutions, I've been using gain Tongue ). Be careful if you are going to have temperature variations it will change the amount of light coming out of your LED. Check your datasheets. Unfortunately I've never found much written on how to compensate for this...

I agree with solutions, having more than one wavelength of light hitting the photodiode will make things harder to characterize.
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mare69
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« Reply #15 on: November 27, 2012, 07:24:48 19:24 »

I made some tests. Photodiode was BPW34 (I have "few" of them from one closed project, about 1k). I used OPA381 with 5MΩ||4.7pF feedback.

Light was generated with 10Cd white LED, reflected into photodiode. After removing DC component (simply oscilloscope set to AC), I've got some noisy, but useful signal, about 4mVpp from my heart beat. Sorry for poor photo, the scope was not connected to PC.

That's just the first experiment. I'll post further progress...

M.
« Last Edit: November 27, 2012, 07:27:45 19:27 by mare69 » Logged
borberk
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« Reply #16 on: November 27, 2012, 08:26:41 20:26 »

What about Monolithic Photodiode and Transimpedance Amplifier like OPT101 or OPT210 and OPT211?
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Gallymimu
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« Reply #17 on: November 27, 2012, 09:14:49 21:14 »

I've got some noisy, but useful signal, about 4mVpp from my heart beat. Sorry for poor photo, the scope was not connected to PC.


Building a Pulse/Ox?
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mare69
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« Reply #18 on: November 27, 2012, 10:44:32 22:44 »

Building a Pulse/Ox?

No, just experimenting with possibilities for low cost, short range photoplethysmograph.

What about Monolithic Photodiode and Transimpedance Amplifier like OPT101 or OPT210 and OPT211?

Looks nice, but I have access to the photodiode process.  Grin
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solutions
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« Reply #19 on: November 27, 2012, 11:43:27 23:43 »

Photoplethysmograph optical sensors are very cheap: http://www.dealmed.com/Nellcor-Compatible-Disposable-SPO2-Sensor-Adult_2?utm_medium=CompCPC&utm_source=nextag&utm_campaign=CSS&gdftrk=gdfV21435_a_7c1031_a_7c4310_a_7c87838

I suppose there's method to your madness when you say "short range"
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mare69
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« Reply #20 on: November 27, 2012, 11:51:34 23:51 »

That's for transmissive method. Reflective is more flexible and it can operate from the distance.
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