Timeline for Increasing sensitivity of photodiode amplifier
Current License: CC BY-SA 4.0
24 events
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| Aug 2, 2021 at 20:08 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jul 1, 2021 at 23:47 | answer | added | user173271 | timeline score: 1 | |
| Jul 1, 2021 at 22:03 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jan 15, 2021 at 13:23 | comment | added | D.A.S. | The OA appears to be a good choice for low offset and high Aol and low noise pulsed low C FET switch can replace the 1M with more gain and less offset with suitable f for noise rejection | |
| Jan 15, 2021 at 13:17 | comment | added | D.A.S. | LEDs are also PD’s when reverse biased to 5V max. Each reduction from 160 deg /2 almost doubles the sensitivity . So 0.5mA/mW is boosted . The almost is due to lens loss but the x2 factor is from magnification. By sanding the lens surface slightly , you create some diffusion as as well as reflection loss so experiment with that to see what gain you can achieve. It won’t be 2x since the source is not a wide beam. Perhaps a 10x glass lens from a microscope may work. | |
| Jan 15, 2021 at 12:16 | history | edited | Miakatt | CC BY-SA 4.0 |
Proposed solution circuit.
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| Jan 15, 2021 at 9:59 | history | edited | Miakatt | CC BY-SA 4.0 |
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| Jan 15, 2021 at 0:22 | comment | added | D.A.S. | the Hammatsu is only 1.2mA/mW and you can get an 8deg IR LED that starts at 0.5mA/mW multiplied by 8 or so | |
| Jan 14, 2021 at 22:51 | answer | added | WhatRoughBeast | timeline score: 0 | |
| Jan 14, 2021 at 21:23 | comment | added | user1850479 | Why would you have to get a lens made? Just buy one from a catalog. | |
| Jan 14, 2021 at 20:56 | comment | added | Miakatt | @TonyStewartSunnyskyguyEE75. We'd have to get a lens made specifically. The PD is 80um diameter. But i agree, if this was easy to get, it would be the first thing I'd try. BW, initially, slow. 100's of Hz. | |
| Jan 14, 2021 at 20:54 | comment | added | Miakatt | @user1850479. Thanks. I'll look in to that and see if I can find an op-amp with the same footprint as the OPA4350. Thanks for the suggestion. Sorry. Can't give info of the system as it's company property. :-/ | |
| Jan 14, 2021 at 20:53 | comment | added | Miakatt | @Andyaka. For now, it's DC. But eventually it will be running at a few 100's Hz, or hopefully 10's of kHz. For now, I'm keeping it simple. | |
| Jan 14, 2021 at 20:33 | history | edited | Miakatt | CC BY-SA 4.0 |
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| Jan 14, 2021 at 19:03 | comment | added | D.A.S. | What is your BW spec? A lens can gain much | |
| Jan 14, 2021 at 18:56 | answer | added | Matt | timeline score: 1 | |
| Jan 14, 2021 at 15:19 | comment | added | user1850479 | In addition, a diagram of your imaging system would be very helpful. | |
| Jan 14, 2021 at 15:18 | comment | added | user1850479 | 4 fA per root hz current noise on your opamp isn't terrible, but you could also do better, which would allow you to have more gain in the first stage without adding additional noise. To pick a random opamp, the OPA657 is 1.3 fs per root hz, so 3x better. There may be even better choices. | |
| Jan 14, 2021 at 13:56 | comment | added | Math Keeps Me Busy | "The 2nd stage is a voltage amp with a feedback of 10kΩ." As @Bimpelrekkie says, your second stage is another TIA. Also 10k\$\Omega\$ is not a quantity of feedback for a voltage amplifier. | |
| Jan 14, 2021 at 12:57 | review | Close votes | |||
| Jan 29, 2021 at 3:01 | |||||
| Jan 14, 2021 at 12:22 | history | edited | Miakatt | CC BY-SA 4.0 |
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| Jan 14, 2021 at 12:12 | comment | added | Andy aka | Is the light modulated or is it just a slow varying intensity? | |
| Jan 14, 2021 at 11:47 | comment | added | Bimpelrekkie | The common way to use a photodiode is using it in reverse bias, I do not see any bias voltage applied here. The first stage is a Trans Impedance Amplifier (TIA), as the output of a photo diode is a current that makes sense as a TIA has a current input and outputs a voltage. Your 2nd stage is another TIA. That makes no sense as the output of the 1st stage is a voltage, not a current. So basically the 2nd stage does nothing. | |
| Jan 14, 2021 at 11:27 | history | asked | Miakatt | CC BY-SA 4.0 |