LTC6268-10 1khz bandwith application

Hi,

Iı am new in this forum. It is very nice to be able to ask questions. Thank you in advance.

I bought LTC6268-10 for a trans-impedance amplifier application for LIDAR. The laser emits in 10ns pulse and bandwidth of the laser is 1 khz. I have chosen LTC6268-10 because of its high slew rate. When I try to simulate the results according to the bandwidth of 1khz, the program with the link https://tools.analog.com/en/photodiode/ od analog devices says: it is fast opamp so low SNR. It is unsuitable. Can ı use this LTC6268-10 for 10ns pulse width 1kz frequency photodiode signals? Does it have too much noise for my application? Does the propagation delay of LTC6268-10 change so much according to the current of the avalanche photodiode.

Thanks.

Regards

0 GlenBrisebois

on Apr 6, 2020 7:09 PM
Hi Cesur: If your pulse is 10ns, then you probably want 100MHz bandwidth as a minimum, to capture that pulse. This is true even if the repetition rate of the pulse is only 1kHz.
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0 cesur on Apr 9, 2020 7:28 AM in reply to GlenBrisebois

Hi,

Thank you for your answer. Yes, it is true, I want 100 Mhz bandwidth to capture 10 ns pulse. But repetition is 1khz. Does the noise be too much to work with? The online simulation program offers 24.9 k feedback resistance and a 100 fF feedback capacitor to get 96 Mhz bandwidth. I guess the minimum output of the trans-impedance amplifier will be 10 mV when the laser light comes from 10 meters. Does the noise of the opamp can prevent me to read that signal because the simulator says fast opamp is not proper for low-frequency application.

Thank you.
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0 GlenBrisebois

on Apr 9, 2020 8:26 PM in reply to cesur
Hi Cesur: If you let me know the PD capacitance, then I will be able to calculate the LTC6268 output noise in a bandwidth of 100MHz with 24.9k gain.
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0 cesur on Apr 10, 2020 3:24 PM in reply to GlenBrisebois

Thank you, 2.2 pF at 20V reverse bias.

Regards
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0 Hooman

on Apr 13, 2020 9:21 PM in reply to cesur
Hi cesur and Glen,

I'm thinking you can use LTspice to simulate your circuit.

LTspice shows about 100MHz BW with the conditions you've specified. The RMS noise over the entire bandwidth simulates to around 2.9mV_RMS, as shown below.

Please take a look.

Simulation file:

LTC6268-10 TIA EZ 4_13_20.asc

Regards,

Hooman
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