S-52

The Tektronix S-52 is a pulse generator head compatible with S-series sampling units like the 3S2, 7S11, and 7S12.

It puts out a 200 mV pulse into a load of 50 Ω. The pulse has a rise time of 25 ps or less. The output is an SMA connector.

In addition to the main pulse output, the S-52 also produces a pre-trigger pulse 85 ns before the main pulse. The delay is generated with a digital counter, and jitter between the pre-trigger pulse and the main pulse is specified as less than 10 ps. The pre-trigger pulse uses a BSM connector.

Key Specifications

Rise time	< 25 ps
Output amplitude	200 mV into 50 Ω (SMA)
Output impedance	50 Ω «reverse terminated» (i.e. having controlled source impedance)
Pre-trigger output	85 ns before main pulse (jitter < 10 ps), +1 V into 50 Ω (BSM)

Internals

The S-52 generates the main output pulse using a 50 mA low-capacitance tunnel diode with part number 153-0040-00.

The S-52 is similar to the S-50, but the S-50 has twice the pulse amplitude. The reason for this is that the S-52 has a 48 Ω resistor between the output tunnel diode and the output connector providing back termination, while the S-50 has no such resistor. Although the S-52 produces a smaller pulse, its output impedance is much better controlled than that of the S-50, and the output resistor may also provide some limited protection for the output tunnel diode.

The S-52 uses a 156-0048-00 transistor array in the timing board.

Links

• Tek S-52 page @ amplifier.cd
• Tektronix S-52 @ barrytech.com

See Also

• 25ps Push-Pull Pulse Generator

Pictures

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  S-52 front

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  S-52 front A-prototype

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  S-52 pulse generator and S-6 sampling head in a 7S12 TDR/Sampler plugin

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  A-prototype of S-52

Internal

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  A1 Timing board (right)

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  A3 Trigger board (left)

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  A2 Tunnel Diode Control board (center)

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  Tunnel diode mount

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  Tunnel diode mount, detail

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  Schematic

Measurements

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  TDR "Self Portrait" — pulse reflected on S-6 "through" path (approx. 120 ps one way)

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  7S12 displaying the incident pulse from an S-52 (nom. < 25 ps) through an S-6 head (nom. < 30 ps). Displayed rise time ~35 ps confirms spec.

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  Full pulse pattern of a 7S12/S-52 in real time (top trace) and sampled (bottom trace) shown simultaneously on 7844. 7S12 trace at slowest possible sweep.

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  S-52 pulse in real time (top trace) and sampled (bottom trace) shown simultaneously on 7844. Approximately equal time scales.

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  Full pulse pattern of a S-52 (A-prototype) , driven by 3S6 (freerunning)