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Show us your square wave

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tggzzz:
OK, here's the edges from a very simple pulse generator:

* the source is 5V with no load, but obviously it is used to drive 2.5V into the scopes' 50ohm input
* 4GHz LeCroy HDO4904, connected directly to the scope input with a BNCfemale-BNCfemale adaptor
* 1GHz Agilent MSOS104A, connected via a 1m piece of coax of untested quality
It looks like the 10%-90% risetime is 256ps with a 6.3% overshoot, and the falltime is 453ps with a 3.8% overshoot.

Considering the simplicity of the circuit, that is remarkably fast. It is a simple demonstration that modern jellybean logic (74LVC1G*) generates significant power into the microwave waveband - and hence RF practices are appropriate.

In this circuit a major contributor to the performance is the decoupling capactors, especially the 0V/5V planes and short wide wires, and not forgetting that MLCCs have a very significantly reduced capacitance when there's a DC bias voltage.

My apologies for the quality of the photos; they had to be taken relatively quickly and in non-ideal conditions.

MaxFrister:
Measurements Corporation Model 71 Square Wave Generator displayed on a Hewlett Packard model 122AR.

T3sl4co1l:
Weird, the sweep linearity on that scope seems to be wrong?

Tim

Microcheap:
Only fine equipment in this thread so I've decided to bring some "toys" to compare. The first is an unlocked Hantek HDG2002B, the output is a 15MHz 2Vpp signal with a 50ohm pass through terminator on scope and then a 1MHz signal directly connected on the scope using a BNC cable.
The second function generator is a MHS-5200A, both signal showed are connected to the scope with a BNC cable only.

dzseki:
Source for all tests below: EMG 12563 (an old hungarian made) ECL pulse generator the rise time was measured to be 425ps (including the scope's self rise time) with a LeCroy WavePro 725 2.5GHz 40GS/s scope. The interconnect cable was (the same for all testing) a vintage Amphenol RG223U coax 1m long.

Yokogawa DL1740 4CH 1Gs/s 500MHz:

HP 54503A 4CH 20Ms/s 500MHz, the measured rise time varies somewhat between the channels, but for the good...

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