Is there a general rule of thumb for high(ish) voltage (ie. 100V to 140V range), but low leakage (Vce and maybe Vbe) BJT transistor type. ...Or is the higher voltage the rule of thumb to find lower leakage type.
** Low leakage, <15nA **
**When searching that transistor model***
PS. If we still try to stay on "general purpose" category.
If it meets the datasheet, and your application works based on datasheet information, then you're fine.
Is there a general rule of thumb for high(ish) voltage (ie. 100V to 140V range), but low leakage (Vce and maybe Vbe) BJT transistor type. ...Or is the higher voltage the rule of thumb to find lower leakage type.
** Low leakage, <15nA **
**When searching that transistor model***
PS. If we still try to stay on "general purpose" category.
Leakage depends more on area, construction, processing, and temperature than voltage rating. For small signal transistors, it is only tested down to a level of 10s of nanoamps because that covers almost all applications and a more sensitive test would take longer.
Voltage rating has more of an effect on recovery time.
A thorough search will turn up transistors tested down to 10 nanoamps but I think of low leakage as 10 picoamps and lower which I have had no trouble finding in common parts like the 2N3904.
It would be interesting to know if the garden variety actually do have different internals between models or are they actually just from one outcome from a machine and then sorted to meet different key specifications of garden variety part numbers. I wouldn't be too surprised (without having even general knowledge of semiconductor production) if this would be the case looking at how close the specks are in many parts.
If it's not on the datasheet, you have to test it yourself. Fine for breadboarding, or small run test equipment, say. Not so great for production.
Wouldn't life be easier if, instead of the JEDEC/whatever part numbering scheme evolving, we'd had something like the National book. Here's the set of dies, here's the parameters we actually test and here's the bins we put them into and the part numbers for those bins.
I still find myself going to the (defunct) National databook to find a suitable part from time to time just because the layout by process makes it easier to navigate.
the 150 volt 2N5401 and 2N5551 would be more suitable.
Or the similar MPSA46, or whatever they are, from that family. MJE350 and complement are also quite popular for audio (driver stage), though the datasheet is sorely wanting. I think On Semi makes a detailed datasheet? Or, there are equivalent parts with good data out there, shop around.
Did you mean the MPSA43/MPSA93? They are a little slower.
The Motorola/On MJE371/MJE521 are the same way. They are recommended for specific applications but lack a full set of specifications. I ran across them when doing a search for fast TO-126, TO-225, and TO-220 parts to use in high performance regulators.
The BD135 through BD140 are like that also. The ST and Fairchild datasheets say nothing about dynamic performance but there are SavantIC Semiconductor (who?) datasheets which say 190 MHz for the NPNs and 160 MHz for the PNPs. What?
How disturbing it is that VHF means very high frequenzy in a 30 MHz to 300 MHz range while every dog collar today transmit in Gigahertz range Wifi. Anyone else annoyed.
Band name | Abbreviation | ITU band number | Frequency | Wavelength | |
Extremely low frequency | ELF | 1 | 3–30 Hz | 100,000–10,000 km | |
Super low frequency | SLF | 2 | 30–300 Hz | 10,000–1,000 km | |
Ultra low frequency | ULF | 3 | 300–3,000 Hz | 1,000–100 km | |
Very low frequency | VLF | 4 | 3–30 kHz | 100–10 km | |
Low frequency | LF | 5 | 30–300 kHz | 10–1 km | |
Medium frequency | MF | 6 | 300–3,000 kHz | 1,000–100 m | |
High frequency | HF | 7 | 3–30 MHz | 100–10 m | |
Very high frequency | VHF | 8 | 30–300 MHz | 10–1 m | |
Ultra high frequency | UHF | 9 | 300–3,000 MHz | 1–0.1 m | |
Super high frequency | SHF | 10 | 3–30 GHz | 100–10 mm | |
Extremely high frequency | EHF | 11 | 30–300 GHz | 10–1 mm | |
Tremendously high frequency | THF | 12 | 300–3,000 GHz | 1–0.1 mm | |
Ridiculously high frequency | RHF | 3–30 THz | 100–10 μm | ||
Fantastically high frequency F***ing high frequency | FHF | 30–300 THz | 10–1 μm | ||
Obscenely high frequency ** Optically high frequency | OHF | 300–3,000 THz | 1–0.1 μm | ||
Preposterously high frequency | PHF | 3–30 PHz | 100–10 nm |
I have started to think that I stock a few hundred
general purpose through hole transistors (an investment of a few tens of bucks). To be sure I will have them to tinker around as to me it seems that the jellybean variety is vanishing or vanished already from THTs.
I'm mostly thinking of small signal, low freq (<200MHz), throw in buffer etc. general purpose uses of tinkering and maybe slobby repair or hack here and there.
BJTs:
BC547B(npn) & BC557B(pnp) comes to my mind.
Is there other worth to look that are still readily available.
Darlington models to maybe look at?
.
JFET
Is there cheapish (<$0.50 ) replacement for 2n4117 other than mbf4117(smd). It seems to be pretty alone in fart detector range.
MOSFET
For logic level switching use. Any ideas, in leds/signals on/off range of power. Should be also as robust as possible for ESD and ideally should have the protective diodes. 2N7000 ?? or were it JFET&BJT hybrid, hmm.
Known matched pairs (for that random differential stage) that wouldn't cost arms and legs and could still be found as THTs. ..none or should I look from IC listings..
Any other than TO-92 cases to look at for jellybean THT parts. Metal cans seems to be premium only now.