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    how to measure current in the TIA

    For example, I have two feedback TIAs (with photodiode connected). I want choose the one with large input current signal, and the shunt down the other. So, I have to measure the average current through the TIA, by means of measure the received optical power. Does anybody know how to perform...
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    Low speed Clock and Data Recovery

    Hi, all I am designing a optical receiver with 2 Mbps. However, I could not find an Clock and data recovery (CDR) in that speed, and also CDR consumes a lot of power. Therefore, I am trying to find a clocked comparator to perform the function of the CDR, since the continues comparator will...
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    FPGA receice LVDS signal

    Hi, all I am using Altera Cyclone lV to receive the "LVDS" data from a clock and data recovery (ADN2813) Below is my schematic,. what I did in the PFGA is, let the pin work as "LVDS" or "LVDS bus", like below: I can successfully receive the data. see "y7" and "rx", they are exactly...
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    Looking for a Fast LED

    Hi, all I am looking a fast LED for optical communication, the data rate is 50 Mbps. So far, the fastest one I can see is SFH4501 with the rise/fall time of 10 ns. So, my question is 1, can this LED be used for 50Mbps communication? 2, is there some faster LED...
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    Single ended to differential in transimpedance amplifier

    Hi, all Does anybody know how to play a single ended to differential conversion in the transimpedance amplifier ? Just like the red circle in the Figure. My input analog signal is 50MHz, amplitude is about very low, about 1mV. So, should I use a balun or fully differential amplifier like...
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    ISI in optical link

    Hi, all I get a question for ISI ( inter symbol interference) in optical link. In Razavi'S book,<design of integrated circuits for optical communications> P65, Fig4.2 (b) It says that if the bandwidth of the receiver is 1/4 of the data rate, then voltage decrease due to ISI is roughly...
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    Amplifier between TIA and limiting amplifier ?

    Hi, all I am designing a TIA like this, It is single ended, therefore, I think I need a single end to differential amplifier and then connect to the limiting amplifier (differential input). see red circle in the following figure. Does anybody have a suggestion for this amplifier...
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    Rise time of photodiode?

    Hi, all Does anybody know when the photodiode datasheet says, a photodiode has a rise time of, i.e, 5ns. It means "transit time is 5ns" or " together with the RC network (50ohm load)", the whole rise time is 5ns? Thanks in advance
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    Depletion layer thickness?

    Hi, all Does anybody know how large is depletion layer width for photodiode? For example, for photodiode S3590-06, which has cut-off frequency of 20MHz, and its depletion layer width is 500um. But what about the other photodiode, for example, a photodiode with 100MHz or 50MHz? I know...
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    where to find the DC-DC converter for APD ?

    Hi, all I just want to build an avalanche photodiode (APD) based optical receiver. I want to use AD1500-9 from "first sensor". https://www.first-sensor.com/en/datasheet/501208 The question is where to find the DC/DC to bias this APD? The datasheet says that the optimal gain is 50-60...
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    why InGaAs photodiode always small than silicon photodiode?

    Hi all Does anybody know why InGaAs photodiode is always small than silicon photodiode? For example, **broken link removed** from hamamatsu, it has diameter of 1mm, and 90pF capacitance. and cut-off frenquency is 35MHz. while for a silicon photodiode, for example, **broken link removed**...
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    what does directivity stand for photodiode?

    Hi, all I get a question for "directivity" for the photodiode? Below is the "directivity" for S2506 from hamamatsu. Does it mean when the light is incident to the photodiode Vertical. I= P*R , where I is the current, and R is responsivity , unit in A/W. And when the light...
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    How to measure the current through the photodiode

    Hi all For example, I am using a TIA to drive two photodiodes. And I want to know how large of the current generated through each photodiode, and this measurement circuit will not have a effect on the TIA/photodiode pair. I know there is some kind of TIA, which can measure the current, for...
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    Photodiode package choose

    Hi, all I have two questions about the photodiode package. 1, some of the photodiodes are packaged in plastic, for example **broken link removed**in T1 or BPV10 in T-1¾. what does this "arch“ sharp package for? provide a wider angle and a optical gain? I put my understanding in the...
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    How to compare multiple voltages ( II )

    I try to simplify my questions in the last thread , then I realized I failed... Here is my original question.... I try to build a photodiode array which contains 4 photodiodes. Each photodiode is connected with its own TIA (transimpedance amplifier), and then connected to LA (Limiting...
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    how to compare multiple voltages?

    Hi, all I get several (4-16) DC output voltages, all ranging from 0-3.3v. and I want to compared all these DC, and choose the highest one as the input signal of my next stage. what kind of devices should I choose? I searched for "multiple voltage comparator" but found nothing. Thanks
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    How can I design a Return to Zero optical link

    Hi, all I want design a Return to Zero optical link with variable duty cycle. I started it from 50% duty cycle. Following is my block diagram. Basically, I use a and gate to generate 50% duty cycle Return to Zero(RZ) signal and use D flip flop to recover the signal to...
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    is there some RZ-to-NRZ convertor ?

    Hi , all I can find NRZ-to-RZ Converter, for example, HMC706LC3C or **broken link removed** but is there some RZ-to-NRZ convertor ? or I have to use a D flip-flop to design by myself ? Thanks
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    is there some IC can change the signal from Non-return-to-Zero to Return-to-Zero ?

    Of course I can use "And gate" to get a 50% return to zero data, but i want to change to duty cycle of output data from 10-50%, So, is there some IC can do this job ?
  20. T

    how to delay the signal ?

    Hi, all the input is 50MHz clock signal. I want to delay this clock signal from 1n- 10ns Of course, I can use two Inverter to Achieve this delay, but the delay time is not controlled. but is there some IC, I can controlled the delay ???

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