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.
| 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 |
| Output TD tripper scheme | current pulse through TD bias transistor | snap-off diode capacitively coupled to TD, like in 284 |
