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The S4 sampling plug-in head provides one 50-ohm SMA input port with a 25ps risetime and a bandwidth of 14.5GHz. The unit provides a trigger pickoff signal for internal triggering and is specified for less than 5mV of noise. The S4 is the fastest of the S-series plug-in samplers. A interesting comparison of different sampling heads is found in [http://www.picosecond.com/objects/AN-02a.pdf "AN-3042a, Revision 1, 2/89"]. 
{{Plugin Sidebar
|manufacturer=Tektronix
|series=7000 and 3S series sampling heads
|type=S-4
|summary=Sampling Head
|image=Tek-s-4.jpg
|caption=S-4 head
|introduced=1968
|discontinued=1990
|designers=George Frye
|manuals=
* [[Media:070-0896-00.pdf|Tektronix S-4 Manual 1969]] (OCR)
* [[Media:070-0896-01 march 1985.pdf|Tektronix S-4 Instruction Manual, Revised March 1985]] (OCR)
* [[Media:070-0896-01.pdf|Tektronix S-4 Instruction Manual, Revised October 1986]] (OCR)
* [[Media:Frye s4 gate.pdf|George Frye's Explanation of S-4 sampler in October 1968 Service Scope]]
* [[Media:Tek s-4 fcp april 1969 - OCR.pdf|Tektronix S-4 Factory Calibration Procedure, April 1969]] (OCR)
}}
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.  


The S4 sampling gate is based upon a traveling wave trapped-charge transmission line in which the sampling window is set by the propagation time of 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.
{{BeginSpecs}}
{{Spec | Rise time | 25 ps (35 ps observed with [[S-50]] or [[S-52]]) }}
{{Spec | Bandwidth | 14.5 GHz }}
{{Spec | Input impedance | 50 Ω (terminated [[SMA connector]])}}
{{Spec | Input voltage | 1 V<sub>p-p</sub> (operating) }}
{{Spec | Maximum input | ±5 V max. non-destructive  }}
{{Spec | Noise | < 5 mV}}
{{Spec | Features |
* trigger signal pick-off for internal triggering
}}
{{EndSpecs}}
 
==Internals==
The [[Sampler#Six-Diode_Sampler|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.
The sampling diodes are housed in a special coaxial connector that provides a high bandwidth signal path.
During the development of the S-4, the velocity gate theory was tested using
a length of transmission line between diodes.
This led to an aperture time that depended upon twice the propagation delay of the length of transmission line.
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 pliers.
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 0.75 mm².
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.
==Prices==
1979: $1,435 (~$6,000 in 2023 dollars)
According to an [[Media:Tek Schottky Diodes Memo rot.pdf|internal memo]], annual sales were estimated at 150 units in 1979.
==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==
<gallery>
<gallery>
Image:S4_top.jpg|Top view of the S4 plug-in
Tek-s-4.jpg
Image:S4_left.jpg|Left view
Tek s4.jpg
Image:S4_right.jpg|Right view
S4_top.jpg | Top view of the S4 plug-in
S4_left.jpg | Left view
S4_right.jpg |Right view
S4 schem.png | Schematic
Tektronix-S4-sampler-board-strobe.jpg | Sampler board, strobe side
Tektronix-S4-sampler-board-preamp.jpg | Sampler board, preamp side
Tektronix-S4-sampler-board-hybrid.jpg | Sampler board, disassembled with parts orientation
Tektronix-S4-hybrid-internal.jpg | Microphotograph of sampler hybrid
S-4_B15_prototype.JPG | S-4 B-prototype, no difference to standard S-4
Tek s-4 in 7s11.jpg | S-4 in [[7S11]]
7s11-s4.jpg | S-4 in [[7S11]]
</gallery>
</gallery>
==Parts==
{{Parts|S-4}}
[[Category:7000 and 3S series sampling heads]]

Latest revision as of 06:16, 30 January 2024

Tektronix S-4
Sampling Head
S-4 head

Compatible with 7000 and 3S series sampling heads

Produced from 1968 to 1990

Manuals
Manuals – Specifications – Links – Pictures

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 (35 ps observed with S-50 or S-52)
Bandwidth 14.5 GHz
Input impedance 50 Ω (terminated SMA connector)
Input voltage 1 Vp-p (operating)
Maximum input ±5 V max. non-destructive
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.

During the development of the S-4, the velocity gate theory was tested using a length of transmission line between diodes. This led to an aperture time that depended upon twice the propagation delay of the length of transmission line.

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 pliers. 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 0.75 mm². 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.

Prices

1979: $1,435 (~$6,000 in 2023 dollars)

According to an internal memo, annual sales were estimated at 150 units in 1979.

Links

Pictures

  • Top view of the S4 plug-in

    Top view of the S4 plug-in

  • Left view

    Left view

  • Right view

    Right view

  • Schematic

    Schematic

  • Sampler board, strobe side

    Sampler board, strobe side

  • Sampler board, preamp side

    Sampler board, preamp side

  • Sampler board, disassembled with parts orientation

    Sampler board, disassembled with parts orientation

  • Microphotograph of sampler hybrid

    Microphotograph of sampler hybrid

  • S-4 B-prototype, no difference to standard S-4

    S-4 B-prototype, no difference to standard S-4

  • S-4 in 7S11

    S-4 in 7S11

  • S-4 in 7S11

    S-4 in 7S11

Parts

Some Parts Used in the S-4

Part Part Number(s) Class Description Used in
152-0335-00 152-0335-00 Discrete component step recovery diode S-4 • S-6
152-0335-01 152-0335-01 Discrete component 150 ps step recovery diode 1502 • S-2 • S-4 • S-6
155-0001-00 155-0001-00 Hybrid integrated circuit gate assembly S-4
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