Other Parts Discussed in Thread: TINA-TI, OPA838
Hi,
I am using OPA657 for my transimpedance amplifier.
Can i read continuous laser signal with this circuit?
Best regards.
Harun
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Morning Harun,
Looks pretty good to me, couple of comments,
1. Don't need R10, that just adds noise
2. Don't need the bias current cancellation network on +IN, the OPA657 is a JFET input device so no bias current matching, just ground +IN
3. Stability is the next thing, and would need the estimated D2 capacitance for that that,
I reviewed decomp op amps and design application (including this one) in this article, If you cannot read the tables and figures let me know and I will attach a pdf,
Hi Harun,
I found this datasheet for the PIN-220D:
A simulation with TINA-TI yields the following results:
Kai
Hi Michael,
Thank you for your help. Minimum pulse width of laser pulse is 300 ns. So the bandwidth should be around 6.7 MHz.
Best regards.
Harun
Hi Kai,
Thank you very much for simulation source. It is very useful for me. I will examine.
Best regards.
Harun
Hi Harun,
the OPA657 is really really fast. Follow the guidelines discussed in section 10 and 11 of datasheet. And it would the best to adopt the layout example given there.
Kai
Hi Michael,
I want to ask another question. We discussed ambient light rejection circuit in below link.
https://e2e.ti.com/support/amplifiers/f/14/t/875831
I am trying the circuit you recommend. What is the purpose of 1.5V DC bias? Can i reduce it to 0V?
Best regards.
Harun
Oh, well that was a single supply design and I was holding the Zt stage pins in range headroom wise with the 1.5V reference - if you are bipolar supply on both, you can make that gnd - if there is a 2nd stage to get to a differential ADC with an FDA, you can stay at ground there and single supply in the FDA.
I worked out a pretty full example of that in the OPA838 introduction time period in this article,
https://www.edn.com/controlling-spot-and-integrated-noise-in-a-two-stage-transimpedance-design/