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
Pretrigger to pulse jitter	15ps	10ns
Pulse repetition rate	25kHz	120kHz
Trigger (with pulse) output	yes, 200mV into 50 ohms	no
Output TD tripper scheme	current pulse through TD bias transistor	snap-off diode capacitively coupled to TD, like in 284

• Tektronix S-50 Manual (46MB, PDF)
• Tektronix S-Series Sampling Heads (195MB, PDF)

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  block diagram

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  schematic

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  front view