TIDA-00663: The transimpedance to replace OPA857

user6077167

Part Number: TIDA-00663
Other Parts Discussed in Thread: OPA857, TDC7200, OPA355

Hi:

In this application of TIDA-00663, we only need to detect if there is laser light to be echoed back, no need to care about the signal to be amplified accurately.

Then, what main parameters should we care about when selecting the transimpedance OP AMP?

If I want to replace the OPA857 with another transimpedance OP AMP, can you help suggest some chips?

Usually, what's the gain range of the transimpedance for the TDC7200 ranger?

Thanks

Zhang

over 3 years ago

0 Giovanni Campanella over 3 years ago

TI__Intellectual 1630 points

Hello Zhang,

The design of the TIA will pretty much depends on the photodiode you are going to choose for your application. Have you selected the photodiode for your application?

Once you have selected the photodiode then you need to determine the f-3db which will be dependent on the rise/fall time of your input signal and the feedback resistance which will be dependent on the input current coming from the photodiode. Once you have determined these parameters you can calculate the GBP that will help you to choose the TIA.

Based on your requirements you can easily select the TIA from this table http://www.ti.com/amplifier-circuit/special-function/transimpedance/products.html

In the TIDA-00663, gain be controlled with an MCU through the CTRL pin. By default this is set at 20k.

Let me know if you have additional questions.

Best regards

Giovanni

0 user6077167 over 3 years ago in reply to Giovanni Campanella

Prodigy 220 points

Hi Giovanni:

The photodiode I used is Osram SFH213.

How about if I choose OPA355 as the OP AMP for the application?

thanks

Zhang

0 user6077167 over 3 years ago in reply to user6077167

Prodigy 220 points

Hi Giovanni:

The input signal rise time is about 0.005us, the fall time is about also 0.005us.

From these data, can we say that the input signal bandwidth is about 200 MHz?

thanks

Zhang

0 Giovanni Campanella over 3 years ago in reply to user6077167

TI__Intellectual 1630 points

Hello Zhang,

With a rise time of 0.005us the f-3db would be 70MHz (=0.35/tr). By using the excel calculator whose link is at the end of this blog post given the desired closed-loop TIA bandwidth (f-3dB), RF and CIN, the calculator returns the minimum gain-bandwidth product (GBP) of the opamp needed for the application as well as the value of feedback capacitance which ultimately will help you to select the right TIA for your application.

Let me know if you have additional questions.

Thanks

Gio

0 user6077167 over 3 years ago in reply to Giovanni Campanella

Prodigy 220 points

Hello Giovanni:

Thank you for the reply.

But I can't access the link to find the Excel calculator mentioned by you.

Please help provide the linkage again.

thanks

Zhang

0 Giovanni Campanella over 3 years ago in reply to user6077167

TI__Intellectual 1630 points

Hi Zhang,

Please try this for the blog post:

https://e2e.ti.com/blogs_/b/analogwire/archive/2016/05/06/what-you-need-to-know-about-transimpedance-amplifiers-part-1

And this for the TIA calculator:

https://e2e.ti.com/support/amplifiers/f/14/t/508669

Let me know if you have any problems opening these ones.

Thanks

Giovanni

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TIDA-00663: The transimpedance to replace OPA857