S-50

The Tektronix S-50 is a pulse generator head the produces 400mV pulses with a risetime under 25ps. The pulse output is an SMA connector. The PRETRIG OUT and TRIG OUT signals use BSM connectors.

The output diode is the same one that the S-52 uses, the 153-0040-00. The internal timing circuitry of the S-50 uses two 152-0379-00 tunnel diodes.

Comparison of S-50 and S-52

The S-50 is similar to the S-52, but the output pulse amplitude of the S-50 is 400mV, twice that of the S-52. The S-50's output tunnel diode is directly connected to the main pulse output connector. The S-52 has a 48-ohm resistor between the output tunnel diode and the main pulse output connector, resulting in a 2:1 voltage divider. Another difference between the S-50 and S-52 is that the presence of a TRIG OUT on the front of the of S-50. Both have PRETRIGGER OUT. The pretrigger of the S-50 leads the main pulse by 75ns. The pretrigger of the S-52 leads the main pulse by 85ns. At the circuit level, the S-50 and S-52 differ significantly. Both use a current switch to bias the output tunnel diode when it is in the "armed" state. The S-50 uses another tunnel diode to add a short pulse of current that "fires" the output tunnel diode. The S-52 uses a snap-off diode to generate this firing pulse. Sequencing of events (arming the output diode, firing it, resetting it) is controlled by analog timing circuits in the S-50. The S-52 uses a digital counter and a decoder to generate the internal control signals.

Comparison of S-50 with S-52

	S-50	S-52
Risetime	under 25ps	under 25ps
Amplitide	400mV into 50 ohms	200mV into 50 ohms
Output impedance	varies, not specified	50 ohms
Sequencing of internal events	analog timing circuit	digital state-machine
Pretrigger lead time	75ns	85ns
Trigger (with pulse) output	yes, 200mV into 50 ohms	no

• Tektronix S-Series Sampling Heads (PDF)

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