Hi,
It looks as if you have a higher noise floor with the TLV3501. I see two
effects, both higher slope (usually but not always due to gaussian
noise) and then also a higher systematic noise. The later could be from
power-suppy for instance, but any form of RF and LF frequency pickup.
The actual noise of the TLV3501 I just fail to spot in the datasheet on
a quick look, but also the bandwidth.
I assume that the trigger point is good, that is that you trigger on the
highest slew-rate point of the curve. For a sine that would be at the
through-zero point, but for square-wave it is actually closer to the
previous level for actual signals. A DC blocker and keeping the trigger
close to zero usually suffice. Then just not loosing amplitude going in,
as amplitude convert to slew-rate.
You might benefit of doing spectrum analysis on the data to locate RF
frequencies and track them down in the analog domain.
Consider using amplification stages to increase slew-rate before hitting
an input.
I remember once a design where the hardware guys had an ECL "comparator"
setup so it in one state gave a solid signal but the other acted as a
linear amplifier of all the noise on the board. While it may seem like
adding hysteresis would cure it, it will only cure it for the non-timing
parts (which will be the amplitude part) of the signal where as the
timing part would still be affected. Also, hysteresis shifts the trigger
point to one which has somewhat less ideal slew-rate for timing
purposes. As always the timing/phase and amplitude parts of the signal
is on orthogonal parts.
Cheers,
Magnus
On 2022-06-06 15:19, Hans-Georg Lehnard via time-nuts wrote:
Hi,
I tested the TLV3501 with the HP E1740A TIA and there is a visible
difference. First test an OCXO on reference and directly on the input.
Second test OCXO via the TLV32501 on the input.
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