S-4: Difference between revisions

Revision as of 00:34, 18 November 2016

Template:Plugin Sidebar 2 The Tektronix S-4 is a sampling head for 7000- and 3S-series samplers. It was designed by George Frye and introduced in 1968. It is the fastest of the S-series plug-in samplers.

Key Specifications

Rise time	25 ps (observed with S-50 or S-52, 35 ps)
Bandwidth	14.5 GHz
Input impedance	50 Ω (terminated SMA port)
Input range	operating, 1 V_p-p; max. safe overload, ±5 V
Noise	< 5 mV
Features	trigger signal pick-off for internal triggering

Internals

The S-4 sampling gate is based upon a traveling wave trapped-charge transmission line in which the sampling window is set by the propagation time of a pulse edge through a thick-film transmission line. This technique requires only a sharp pulse edge rather than a precise pulse width, which is harder to generate. The sampling diodes are housed in a special coaxial connector that provides a high bandwidth signal path.

To disassemble the sampler hybrid, first remove it from the sampler board as per the manual. Remove the input connector using a 7/32" wrench and remove the 20 dB attenuator with small plyers. The ceramic board is held to the housing using roll pins that can be pressed out with a 0.030" pin punch. The hybrid has six diodes, each about 0.75mm square. The cathodes are glued to the gold substrate with conductive epoxy and the anodes are wire-bonded (twice) over a gap to the next step in the strobe line. It appears that a standard beam-lead diode may fit across the gap but cleanly removing a failed diode without damaging the substrate would be quite difficult.

Links

Pictures

Top view of the S4 plug-in
Left view
Right view
Schematic
Sampler board, strobe side
Sampler board, preamp side
Sampler board, disassembled with parts orientation
Microphotograph of sampler hybrid

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 * [http://w140.com/frye_s4_gate.pdf George Frye's Explanation of S-4 sampler in October 1968 Service Scope (PDF)]
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-The '''Tektronix S-4''' is a sampling head for 7000- and 3S-series samplers.  It was designed by [[George Frye]] and [[introduced in 1968]]. It is the fastest of the S-series plug-in samplers.  (An interesting comparison of different sampling heads is found in [http://www.picosecond.com/objects/AN-02a.pdf "AN-3042a, Revision 1, 2/89"].)
+The '''Tektronix S-4''' is a sampling head for 7000- and 3S-series samplers.  It was designed by [[George Frye]] and [[introduced in 1968]]. It is the fastest of the S-series plug-in samplers.
 {{BeginSpecs}}
@@ Line 39: / Line 39: @@
 ==Links==
 * [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_special/S4.html S-4 page @ amplifier.cd]
+* [https://kh6htv.files.wordpress.com/2015/11/an-02a-oscopes.pdf James R. Andrews, ''Comparison of Ultra-Fast Rise Sampling Oscilloscopes''. Picosecond Pulse Labs App Note AN-2a, 1989]
 ==Pictures==