Electronic – What are some good circuits for learning about capacitors

NOTE: A lot of this is now outdated, as Tektronix have released some interesting scopes lately (2015).

This started out as a comment, but I'm expanding it to an answer:

Basically, Tektronix is not competitive in the digital oscilloscope market any more.

Your comparison is fundamentally flawed too. You are comparing Tektronix's bottom-of-the range scope to Rigol's middle-of-the-range model.

The actual Rigol scope that best matches that Tektronix scope is the DS1102E.

• Both have tiny, crappy, QVGA (320*240) screens
• Neither have intensity grading.
• The Rigol still has a lot more sample memory, 1 Mpoints vs. 2.5 Kpoints.

Note that the Rigol scope listed above is only US$400!

Really, if you're shopping for a US$500-US$3000 DSO, the only two players on the market even worth bothering to look at (at least at the current time) are Rigol and Agilent. They are the only two people on the market that offer intensity grading (Rigol call it "Ultravision" and Agilent call it "InfiniiVision").

This is a technique that actually measures the time the input waveform spends at each ADC value per X-axis time-step, and actually varies the intensity of the drawn scope trace to reflect the period of time the input spent at that voltage. This produces a display that actually somewhat resembles a traditional cathode-ray oscilloscope. It is absolutely a excellent feature, and I, at least personally wouldn't even consider a DSO that lacked it at this point.

Basically, Tektronix are just not producing DSOs worth looking at. They did have some good DSOs in the early 2000s: they produced a nice, primitive DSO, garnered a significant chunk of market share, and basically then sat there resting on their laurels and stopped innovating. This is supported by the teardowns I've seen of some of their late-model scopes, which were using rather ancient silicon for their processing. _{^{Note that this is changing, but only for Tektronix's higher end. They're doing some really cool stuff with their MSO devices (mixed-signal oscilloscopes). They basically combine a spectrum analyzer and a DSO, and for RF work, they look excellent. They're also $50K+}}.

Then, Agilent came along and basically completely wiped the floor with them in short order, with their much deeper memory scopes, and introduced intensity grading.

Now, Rigol have subsequently come out with a competitive mid-range scope line that makes them also worth considering, together with Agilent.

As far as I can tell, Tektronix's superb reputation should only really be applied to cathode-ray oscilloscopes (I have several, all Tektronix). They really didn't take the transition to digital, and its high innovation rate well at all.

If I were buying a scope now, I would look for:

Absolutely essential at ANY price-point:

• Greater then 100 KPts memory.
• 640*480 or larger screen. _{^{This is why I never bought one of the cheaper Rigol scopes}}

Absolutely essential a >~$1K price-point:

• Intensity grading.

Nice to have:

• High waveforms/second
  • This ranges from merely nice to totally essential, depending on what you are using the scope for. If you're glitch-hunting, you pretty much have to have high waveforms/second rates for decent coverage. The Tektronix scopes are an order of magnitude lower in waveforms/second then the Rigol and Agilent scopes (though the latest ($$$) Agilents are even better).
• Protocol decoding, at least as an option

Coaxial switches, available from places like teledyne and dow-key, have bandwidths from DC -> 20GHz or more, low insertion loss (~0.2dB), 50ohm impedance, long lifetimes, but have slowish (~10ms) switch times and are comparatively bulky and very expensive. They cost upwards of ~$100 each for a single SPDT switch. From my research if you really need DC-high bandwidth they are the only game in town but are extremely expensive to build a switch matrix out of. That said it's most likely going to be much cheaper than purchasing more oscilloscopes if they meet your need.

I would diagram in detail what your switching needs are, insertion loss and insertion delay requirements, determine your bandwidth needs (with timing measurements and a pulse gen do you really needs down to DC? Do you require 50ohm impedance? If not then you probably don't need the bandwidth of coax switches), and go from there. The best and cheapest solution you can get away with will depend largely on those factors.