S-4

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

• S-4 page @ amplifier.cd
• James R. Andrews, Comparison of Ultra-Fast Rise Sampling Oscilloscopes. Picosecond Pulse Labs App Note AN-2a, 1989

Patents that may apply to S-4

Page	Title	Inventors	Filing date	Grant date	Links
Patent US 3629731A	Sampling system	George Frye	1968-07-12	1971-12-21	Sampling • S-4 • S-6

Pictures

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  Top view of the S4 plug-in

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  Left view

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  Right view

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  Schematic

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  Sampler board, strobe side

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  Sampler board, preamp side

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  Sampler board, disassembled with parts orientation

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  Microphotograph of sampler hybrid

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

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  S-4 in 7S11

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  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