S-50

The Tektronix S-50 is a pulse generator head that produces 400 mV pulses with a rise time under 25 ps. 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 400 mV, 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 the presence of a TRIG OUT on the front of the of S-50. Both have PRETRIGGER OUT connectors. The pretrigger of the S-50 leads the main pulse by 75 ns, that of the S-52 by 85 ns.

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.

Specifications

	S-50	S-52
Risetime	under 25 ps	under 25 ps
Amplitude	400 mV into 50 Ω	200 mV into 50 Ω
Output impedance	varies, not specified	50 Ω
Sequencing of internal events	analog timing circuit	digital state-machine
Pretrigger lead time	75 ns	85 ns
Pretrigger to pulse jitter	15 ps	10 ps
Pulse repetition rate	25 kHz	120 kHz
Trigger (with pulse) output	yes, 200 mV into 50 Ω	no
Output TD tripper scheme	current pulse through TD bias transistor	snap-off diode capacitively coupled to TD, like in 284

Pictures

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  block diagram

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  schematic

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  front view