| Electronics > Beginners |
| Jellybean hobbyist general purpose transistors.. |
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| T3sl4co1l:
--- Quote from: orolo on October 13, 2017, 08:23:32 pm ---But there is a catch, that I first heard of from Bob Pease: the higher the beta, the lower the output impedance. It can be seen in this datasheet: the 547A has 55.5k typical output impedance, the 547B 33.3k, and the 547C 16.6k, and it could go as low as 9k!. This can be very important when building current sources/sinks, active loads, etc. --- End quote --- Only relevant to pure current mirrors without degeneration. Tim |
| bd139:
Jellybeans for me. I don't do SMD really. Well I do, but it's done with TH parts :D 2n3904 (gp npn) 2n3906 (gp pnp) 2n2222 (plastic - switch/high Ic) bd139/bd140 (complimentary / med power npn - make nice compliance range current sources/sinks!) j113 (jfet) IRF510 (medium mosfet) bs170/2n7000 (same part! tiny mosfets). BD139 is my favourite if you didn't guess. They are literally the swiss army knife of transistors. Nice package, high Ft (150MHz+), Reasonable Ic, High Vce, quite difficult to blow up, cheap as chips. One thing to note, your average crappy 2 cent Fairchild 2N3904 has a better NF than any BC transistor, including the low noise 549 until you start getting into RF transistors. Keep the gain reasonable and there's a huge mileage in that part. Literally 90% of my designs use just the 2n3904/2n3906. Edit: also I've got a tube each of CA3096 and CA3028. CA3096 is a few well matched transistors in a DIL package. Great for current sources, compensated feedback for log amps. CA3028 is a can package with a diff amp in it which can be reconfigured in more ways that I care to imagine. Makes nice cascode amps etc. Shame they're both obsolete. |
| David Hess:
--- Quote from: T3sl4co1l on October 13, 2017, 05:25:29 pm --- --- Quote from: David Hess on October 13, 2017, 05:54:49 am ---the 150 volt 2N5401 and 2N5551 would be more suitable. --- End quote --- 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. --- End quote --- 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? |
| CJay:
--- Quote from: David Hess on October 14, 2017, 02:26:59 am ---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? --- End quote --- The BD139 makes an excellent little RF power transistor, 2-3W output across the HF bands and probably into low VHF (never tried it above 30MHz), it's not been a secret but it's also not that widely used, people seem to prefer the long obsolete 2SC Mitsubishi devices |
| bd139:
Indeed. Most transistor selection appears to be religion. Recently I stopped someone paying £8 for an OC transistor in a circuit they didn’t understand just to copy it verbatim. A 2n3906 would do the job, arguably better as well! |
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