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| Siglent SDS1000(X) / SDS2000(X) or LeCroy WaveAce (Blackfin) hacks? |
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| tautech:
--- Quote from: KeBeNe on August 14, 2018, 03:50:01 am ---here is my HW mod on 2104x, this changed the 3db limit from around 250Mhz to 350Mhz --- End quote --- That's sounds about right for a 2304X -3dB point. A screenshot I've posted before on the forum plus an additional few for reference. HP 500 MHz sig gen used for all these screenshots. Factory SDS2304X, 100mV signal: 200 and 300 MHz shots below = 1V p-p signal It can be seen in the 500 MHz screenshot (100mV p-p) is past the stability frequency of the internal counter. |
| markus_jlrb:
@tautech could you please provide a sweep picture, if your sig gen is capable of this feature to see the flatness of the BW mod when the caps are removed. Thanks Markus |
| tautech:
--- Quote from: markus_jlrb on August 17, 2018, 08:35:34 am ---@tautech could you please provide a sweep picture, if your sig gen is capable of this feature to see the flatness of the BW mod when the caps are removed. Thanks Markus --- End quote --- Sorry I can't as I don't have an AWG that can sweep to high frequencies. ATM 30 MHz is the best I have. You have SSA don't you ? Maybe that will do. |
| markus_jlrb:
The caps are mounted between the pos and neg output (OPHI/OPLO) of the AD8370 var gain amp. Both lines are have round 50 ohm impedance according to DS (100Ohm diff). Have made a LT-Spice simulation to check the influence of the cap in parallel to the output (Pin 8/9) |
| markus_jlrb:
The LT-Spice file is attached too. To play arround, remove the .txt suffix. The 0.95(V(n002)-V(n004) 5% recuction is due to avoide overlapping of the red curve. bouth sig gens have 1V amplitude so that the difference is 2V and the corresponding voltage at load (ADC) should be 1V without attenuation and influence of the cap. As I do not know the ADC input impadance, I took the same as the gain amp has in the hope the disign is matching the impedances 1:1. The C value is sweeped from 1pF to 10pF to visualize the cap influence - BW reduction. Markus PS.: The simulation was made for 200MHz as I would like to compare with my DSO. |
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