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LMH6724: LMH6724MA

Thomas Kruse
Prodigy 10 points
Part Number: LMH6724
Other Parts Discussed in Thread: LMH6715, , LMH6723, TINA-TI

Hello! This APD (TIA) worked before with one CLC5602IM. As your crosslink table tells me, the alternate part will be the LMH6724 (LMH6715). Well, the result looks like not the same like the older one. There are some riple and peak deforming shape on the falling edge. Looks like over-swing in case of looks like ringing a bit. The not given values beside C12 are not set (not used). IC3B has little gain (around 5) and the second one below around 40. The problem here is an extreme wide dynamic range this little circuitry must fit. Well, the falling edge looks better by increasing R8 to 50R or 75R. Maybe 100 or 200. But to get A of around 40 R15 must set up to less than around 10k ohms to meet the gain of little less than 40 again. some clamping diodes will be usefull for strongest input level to limit them, but we are working with 5ns rise time pulses and pulse width of 100ns or little more. So a clamping diode must be quick here... :-). Obviously using ferritte beads like the MPZ1005 types archives little more signal power than using 10 ohms... Another pre amp. seems to be usefull here to amplify the signal to get old levels back to their original values (with CLC5602IM). Using video amps may be not help here for TIA like preamplification from APD signals... Even one stage should be used only with little gain(s) to around 10 or less. Any ideas are welcome. Kind regards, Thomas

  • 0
    Guru 48395 points

    Well Thomas, starting from the CLC5602, that is just a dual CFA op amp with a lot of gain in the output current stage. There are many alternates to that part, but without a sim file not much to do. Any chance of a TINA file of your intended circuit. Also, you drawing above shows some RC element back to the input but no values? The LMH6723 looks reasonable - quite a lot faster it seems

  • 0
    Guru 140200 points

    Hi Thomas,

    like this?

    thomas_lmh6723.TSC

    Kai

  • 0 in reply to kai klaas69
    Prodigy 10 points

    Hello Kai, thank you so much, yes, this is it. Well, almost. I am not shure if C2 and R3 will take a big advantage of that circuitry. But I will try this. The voltage is fixed to +/-5V. But I'll let you know about tunings here to re-get APD responses in that way. I am using HAMAMATSU photodiodes with around 150V and a resistor of 1k in the footpoint to GND for signal restauration... But thanks - let me try...

  • 0 in reply to Thomas Kruse
    Prodigy 10 points

    Hello, I do not have TINA Tool, using Spice or LTspice XVII or Altium Designer bult in tool. Almost the same... (nearly). Could not gamble around with this, for my "demo" version of TINA this *.TSC seems to be too big. Gave me an error here if I start the sim. But, looks OK so far. The input level of an APD diode is 1k to GND. With 100nF for DC blocking for daylight (sunlight) issues. Dark current I can handle, but sunlight (as we all know) will decrease sensitivity much... Thanks for your work...Cheers, Thomas

  • 0 in reply to Thomas Kruse
    Guru 140200 points

    Hi Thomas,

    not TINA but TINA-TI:

    https://www.ti.com/tool/TINA-TI

    TINA-TI is free Relaxed

    Kai

  • 0 in reply to kai klaas69
    TI__Genius 16561 points

    Hi Thomas,

    If you need help getting up and running with TINA-TI, please let me know.  TI has existing resources for setting up and running simulations on TINA-TI circuits.  I am also available to assist Slight smile.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 10 points

    Hello Alec, yes, got the TINA-TI version. Setup went good. No issues. Try to play around with it the next few days. Try to find out how good this proposal will work for my receiver to look at optimal gain (well, better performance). Try to get its maximum out of my APD. Well, may add additional stages so pre-amp. main-amp and post amp with signal shaper is good here to recover the wanted receiving signals. Come back if I need more support. Thanks for now. Thomas

  • 0 in reply to Thomas Kruse
    TI__Genius 16561 points

    Hello Thomas,

    Sounds good.

    Alec

  • 0 in reply to Alec Saebeler
    Prodigy 10 points

    Hello Alec, do you have experience here? 1) Does it make sense to add another pre-amp for more sensitivity? 2) What do you think are around 106dB of gain? To avoid ringing or swing I may not change R1 R4 that much higher. A few 100 ohms to 1-2kohm should be OK here?. What are the real benefit from C2 R3? A log amp. Integration will help for some delay - and integration, but speed is the goal here. And also to get the ideal working point for lowest and strongest signals. BAV99 and similiar limiter are often not quick enough so I will look for ultrafast limiter to avoid saturation of the following stages. So my first try is to add an additional pre amp now and then I'll check for correct values...Thanks, Thomas

  • 0 in reply to Thomas Kruse
    Guru 140200 points

    Hi Thomas,

    hmm, C2 and R3 are essential for this amplifier to turn it into a TIA (transimpedance amplifier).

    I have spend lots of time to optimize the circuit for a detector capacitance of 1pF. Change a bit C2 and/or R3 and you will see how the performance of the circuit is degrading.

    What is you detector capacitance?

    Kai

  • 0 in reply to kai klaas69
    Prodigy 10 points

    Hello Kai, understood. Well done. 0.5A/W S M=1; ID=100µA VBR: 150-200V. Dark current ID: 1-10nA; Cutoff frequency fc RL=50R: 120MHz; Terminal capacitance Ct: 40pF. x (Excess noise figure 800nm: 0.3; Gain M @ 800nm: 60. Rest is not given... The diode is an Si APD... I will update your *.TSC file and add more given items to finalize the circuitry this weekend, maybe tomorrow if I have time to do... Thomas

  • 0 in reply to Thomas Kruse
    Prodigy 10 points

    Hello Kai, I have my circuitry ready. I would like to upload my TSC, did not know how yet. Try to insert but this will come up inside this text mesage and not as an attached file. Try to look first how this will work. Well, this solves my problem anyway - so I may close this request soon, we may spaek (write) with direct PN or emails? Well, I live close to HAMBURG Germany, and Kai seemst to be also a german name... Anyway to simulate and APD is getting more a current pulse (or voltage pulse over 1k resistor connected to GND and decoupled with a few nF (1-100nF) as an DC-free signal (almost) to these op amps. I come back soon if I checked how to add a TSC-file. Thanks

  • +1 in reply to Thomas Kruse
    Guru 140200 points

    Moin moin Thomas,

    and warm greetings form the romantic Schwarzwald Relaxed

    To publish the TSC-file use the "Insert" feature of this text window. Then click on "image/video/file".

    Kai

  • 0 in reply to kai klaas69
    Prodigy 10 points

    Hello Kai, that is what i thought... OK, thanks for help. I did further tunings and investigations and I am happy with my design now. Well with TINA all looks good for me now. I may not provide my latest TSC file to all of us for now. So I close this file now. I did rework my pcb and I will update you (just in case) later after first real measurements from real physics include weather problems (sunlight - and hot roof heat mirroring (fatamorgana effects) and other (rain).... Thank you again, cheers, Thomas - und Grüße in den Schwarzwald. ;-)