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Sampling diodes: Difference between revisions
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There are at least two kinds of '''sampling diodes''' used in classic Tek | There are at least two kinds of '''sampling diodes''' used in the [[Sampling gate|sampling gates]] of classic Tek gear, GaAs junction diodes and Schottky diodes. | ||
It is easy for these diodes to get destroyed by ESD. They are designed to have low capacitance, which means that a small amount of charge can produce a potentially damaging voltage across the diode. | It is easy for these diodes to get destroyed by ESD. They are designed to have low capacitance, which means that a small amount of charge can produce a potentially damaging voltage across the diode. | ||
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The original diodes are no longer available. When sampling diodes need replacement, there are two options. They can be scavenged from other | The original diodes are no longer available. When sampling diodes need replacement, there are two options. They can be scavenged from other | ||
gear or replacements can be improvised using modern parts. [[Hewlett-Packard|HP/Avago]] makes integrated pairs and quads of high-speed Schottky diodes (e.g. HSMS-28xx series). These are a decent replacement for the original diodes. | gear or replacements can be improvised using modern parts. [[Hewlett-Packard|HP/Avago]] and now Broadcom makes integrated pairs and quads of high-speed Schottky diodes (e.g. HSMS-28xx series). These are a decent replacement for the original diodes. | ||
* [[Media:Tek Schottky Diodes Memo rot.pdf|Tektronix Schottky diodes memo from 1979]] | |||
== Possible modern substitutes == | |||
{| class="wikitable" | |||
|- | |||
! Type of Diode | |||
! Tek sampler | |||
! Measured rise time | |||
! Remarks | |||
|- | |||
| HSMS2822 || [[4S1]] || 320 ps || better than specification and very smooth trace | |||
|- | |||
| HSMS2822 || [[S-2]] || 120 ps || didn't match original specification | |||
|- | |||
| MMDL301 || [[S-2]] || 185 ps || high blow-by, not recommended | |||
|- | |||
| BAT17-04W || [[S-2]] || 110 ps || didn't match original specification, but very smooth trace | |||
|- | |||
| BAT15-04W || [[S-2]] || 70 ps || as specification , smooth trace | |||
|- | |||
| 5082-2835 || [[S-2]] || 130 ps || didn't match original specification | |||
|- | |||
| BAT15-04W & BAT15-099 || [[S-6]] || 80 ps || didn't match original specification | |||
|- | |||
|} | |||
<gallery> | |||
4S1_w_hsms2822_modified.JPG | 4S1 Sampling diode replaced by Avago HSMS2822 | |||
S 2 w BAT15 04W.jpg | S-2 with BAT15-04 | |||
S_6_w_BAT15_04W.jpg | S-6 with BAT15-04W, glued on with Chinese conductive adhesive. | |||
</gallery> | |||
[[Category:Semiconductor diodes]] | [[Category:Semiconductor diodes]] | ||
[[Category:Repair issues]] | [[Category:Repair issues]] | ||