azonenberg changed the topic of #scopehal to: libscopehal, libscopeprotocols, and glscopeclient development and testing | | Logs:
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<azonenberg> So, browsing the amplifier section of Analog Devices
<azonenberg> I see some really cool ultra wide bandwidth RF amplifiers
<azonenberg> But most/all of them are single ended
<azonenberg> Look at the HMC460LC5 for example
<azonenberg> The ADL5580 looks good but the datasheet is a bit iffy regarding common mode ranges
<azonenberg> Making an ac coupled diffprobe is not beyond the realm of plausibility
<azonenberg> lain: So i spent a while more thinking about how to make the AKL-AD1 better
<azonenberg> My new design calls for a cascade of two amplifiers and is AC coupled
<azonenberg> First we have an ADL5580 to convert the differential input to a single ended output, and terminate the other ADL5580 output
<azonenberg> This will then get fed into a Mini-Circuits EHC-24L+ single ended RF gain block
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<azonenberg> S-parameter sim of the proposed amplifier cascade
<azonenberg> including the actual ac coupling cap i plan to use, measured data from an AKL-PT2 standing in for the differential probe input
<azonenberg> then an ADL5580 -> EHC-24L+
<azonenberg> fed by a TCBT-14+ bias tee
<azonenberg> If i can design a bias tee that goes closer to DC without losing high speed performance that would be great but i feel like beating something available COTS from minicircuits will be hard
<azonenberg> The bias tee issue will go away, and low-end bandwidth will drop to a few kHz instead of 10 MHz, if I'm OK with a lot less gain
<azonenberg> Without the second amplifier i'd be at about -15 dB
<azonenberg> The other option of course is to cascade two ADL5580s to get more gain
<azonenberg> Which might actually work nicely
<azonenberg> this eliminates the need for the bias tee
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<azonenberg> With two ADL5580s, I get about -3 dB of nominal gain out to 3 GHz, then it starts peaking. But i suspect the peaking will be largely compensated for by losses elsewhere in the system
<azonenberg> That, and too much gain is an easy problem to solve with a LPF of some sort
<azonenberg> Actually wait, i forgot the 5580 had adjustment for peaking
<azonenberg> With Cpeak=3 and two cascaded 5580s, I get decently flat response out to 4 GHz then it bumps up just a little but i think pcb losses in the amp will eliminate that
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