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Question about transimpedance amplifier

As homework, i should design a transimpedance amplifier (with opamp) for photodetector's front end. I haven't any specification about photodiode's characteristics, so i haven't any information about pratical uses of this system. I can choose arbitrarily any photodiode and hence any application: so i'm looking for any application note, data sheet, reference regardings pratical (and simple) applications. I'm particurlary interested in gas sensing or any domotic application (except light sensor)...any ideas? thanks in advance

Reply to
lionelgreenstreet
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Ultimately anything with a photodiode is a light sensor.

Life wouldn't be fun if you weren't pushing the limits of what's possible, so I would suggest that you pick a photodiode at random, then assume you need to get the highest speed you can out of what you picked.

Domestic applications would include IR remotes; those are modulated at

40kHz so you'd have to have at least that much bandwidth in your system to make it work. And yes, an IR photodetector with an op-amp amplifier is definitely gilding the lily, but just assume that you're designing it for someone's 100-foot long living room/media room. 
--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply to
Tim Wescott

This may be a good tutorial for the OP (can't see his posts) to learn about transimpedance amplifiers:

formatting link

40kHz BW is really easy. On Sunday the remote of the VCR seemed to have croaked. Wife rather unhappy, absolutely wanted to program a movie and we had less than an hour before leaving to visit friends and cook dinner there. So, what's to do? Took an old IR sensor that I scrapped out of a LaserJet III, measured which pins "light up" when turning on the desk lamp, hooked a 10K resistor across and the scope probe to that. Took another remote and was surprised: Plenty of bandwidth. You could nicely see the transmitted packets. Checked the VCR remote, was just wrongly set, bingo.

What also surprised me was that the remote for the DTV converter box used 32kHz instead of the usual 38kHz. Which brings up a question, since I want to (some day ...) build two IR repeaters so we can control stuff from outside on the deck: What is the range in which to expect remotes to transmit? Need that to set the filters.

--
Regards, Joerg

http://www.analogconsultants.com/

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Reply to
Joerg
[snip]

I looked into that a while back. IIRC, It ranges from 32kHz to 58kHz in the pre-manufactured receiver modules.

I'd like repeaters from the patio, my office and the kitchen, into the great room where all the "stuff" is located.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

            When the Islamic Muslims take over Europe
          I will be amongst the first to join the call:
           "It's not our war, it's just a civil war."
Reply to
Jim Thompson

Pretty much the same here. If I ever get around to this I'll send you the schematics, or just publish them. I wish they had used RF for the remotes.

The trick will be in finding strategic locations where mirrors, cabinet doors such help the signal along. Of course I am married, meaning that those things occasionally move.

RF repeaters are an option but that clutters the tables even more. TV, lamp, fan etc.

--
Regards, Joerg

http://www.analogconsultants.com/

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Reply to
Joerg

Try a 9' granite dining room table, and quartz "end tables" that take

4 men to pick up. Things tend to stay put ;-)

I'm thinking hard ball... wall-mounted receiver, wire up to attic and down inside great room wall, transmitter... perhaps hide in picture frame ?:-)

Or route thru ductwork.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
           Liberalism is a persistent vegetative state
Reply to
Jim Thompson

Doesn't work here. Cathedral ceiling, lots of firestops in floors and walls. Tried to route coax there, gave up after several hours and routed outside the house. BUT: I ran structured wiring everywhere. So ...

--
Regards, Joerg

http://www.analogconsultants.com/

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Reply to
Joerg

I have a walk-able attic, plus I'm a master at threading extra wires down the same holes as house wiring ;-)

Though I do think I could do it all line-of-sight plus a few mirrors... shoot to a pot shelf, then down to the equipment.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
           Liberalism is a persistent vegetative state
Reply to
Jim Thompson

The latter is often against code, could mean trouble when you (or your kids ...) want to sell the house some day. Trying to explain isolation signal transformers to a home inspector will likely not work.

A pot shelf? Now, now, Jim, what are you guys ...

--
Regards, Joerg

http://www.analogconsultants.com/

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Reply to
Joerg

C'mon, Joerg--just wire up a Costas loop and phase lock to the input. ;)

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

On short bursts ?:-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
           Liberalism is a persistent vegetative state
Reply to
Jim Thompson

I have a suspicion that some IR protocols don't have enough of a preamble or

0/1 transitions to effectively lock a PLL very well. I imagine you really do need a microcontroller in there that can "help" and even learn the various timing patterns of different remotes...

I was once young and ignorant and didn't appreciate the value of DC-balanced codes... :-)

Reply to
Joel Koltner

Nah, if I had my druthers it'd be two simple bowden wires or just ropes and pulleys. One to push play/stop and the other to push fast forward to skip commercials. But the WAF of this setup ain't high enough ;-)

--
Regards, Joerg

http://www.analogconsultants.com/

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Reply to
Joerg

I skip commercials by not watching TV. On the other hand, I also have one of these:

formatting link
Turns any TV in the vicinity off or on, regardless of brand or model (so far, anyway).

Incredibly useful sometimes.

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

Cool!

--
Regards, Joerg

http://www.analogconsultants.com/

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Use another domain or send PM.
Reply to
Joerg

Useless! No corkscrew ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

        Liberals are so cute.  Stupid as bricks, but cute.
Reply to
Jim Thompson

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