Timeline for stretching ns analog pulses for digital conversion
Current License: CC BY-SA 3.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 18, 2016 at 3:12 | comment | added | kakeh | please find the updated modification and results | |
| Apr 7, 2016 at 13:59 | comment | added | George Herold | @kakeh, So have you read about TIA amps? For your numbers (with some opamp input C and stray.. lets call it 15 pF) with 12 Meg that is a tau of 180 us for a freq of ~1kHz... (ughh) now in the TIA you can pull that up with the opamp and get the mean of the RC freq. and the GBW of the opamp sqrt(1kHz*500Mhz) = ~700kHz. And you'll have tons of noise gain... hence your 4 pF in parallel with the feed back R. You maximum pulse width is nothing like 1ns. (have you tried simulating your TIA?) | |
| Apr 7, 2016 at 2:36 | comment | added | kakeh | photo diode capacitance is around 12pF, I am using the feedback capacitance 4pF in parallel with resistor Rf to reduce the parasitic effects of amplifier, cap is not placed after the opamp stage | |
| Apr 6, 2016 at 14:02 | comment | added | George Herold | @kakeh, Ahh, that is a 500 MHz opamp...What's the photodiode capacitance? I don't see anyway you are getting 1 ns pulses from that. (Got a 'scope shot of the output?) (12 Meg and 4 pf is ~ 50 us time constant!) You can use an led to measure the BW. | |
| Apr 6, 2016 at 2:53 | comment | added | kakeh | currently my TIA is based on OPA656 with a 12M feedback resistor for gain and 4pF feedback cap to reduce ringing effects | |
| Apr 5, 2016 at 16:30 | comment | added | George Herold | Well lower bandwidth, to make the pulses longer will also reduce the voltage. Do you have a schematic for the TIA? Typically increasing the feedback resistor will decrease the BW. | |
| Apr 5, 2016 at 2:59 | comment | added | kakeh | can you please throw some light on design of TIA to give longer pulses,seems pretty interesting, how is that possible ? | |
| Apr 4, 2016 at 14:06 | history | answered | George Herold | CC BY-SA 3.0 |