Favorite BJT transistors, sot-23 and TO-92 equivalents - I
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From: Winfield Hill on 31 Jan 2010 18:36 Gerhard Hoffmann wrote... > >Not sot-23 but sot-223: BFG31 by NXP. Quite nice medium power RF PNP. >There are many good NPNs, but PNPs are scarce. > >BFR93/BFT93 are OK, too. > >NEC NE688xx for low 1/f noise. May not be really better than some >others, but at least 1/f is specified at all. > >BC850/BC860 as the low noise members of the BC847/48/49/50 >and BC857/58/59/60 families. >Fit most sockets, hmmm pads of the other family members, too. > >FMMT 634TA npn Darlington ZETEX/Diodes, Inc. >FMMT 734TA pnp Darlington Excellent. -- Thanks, - Win
From: Winfield Hill on 31 Jan 2010 19:10 John Larkin wrote... > > Are you showing the BFT92 as an NPN? Or is it a posting wrap > artifact? It's a PNP. Oops! Good catch, I meant BFR93 for the NPN. Thanks! > Packaged transistors with Ft's much above 1 GHz are hard to use... > they tend to oscillate in any circuit that's not intended to be an > oscillator. PHEMTs on the other hand usually behave pretty well. Even with damping resistors? E.g., EF outputs look like an inductor, due to the falling beta (assuming a low source impedance). L = Rs / 2pi fT, above the breakpoint frequency, f = fT r_e / Rs. That output inductance resonates with capacitive loads, but a damping resistor can keep Q = 1 max. -- Thanks, - Win
From: Winfield Hill on 31 Jan 2010 19:26 Paul E. Schoen wrote... > > > MPSA06 MMBTA06 PZTA06 MPSA56 MMBTA56 PZTA56 (TO-92 SOT-23 SOT-223) > MJE180-182 MJE170-172 (TO-225AA) > 2N3055 MJ2955 (TO-3) > > Figured that some power types should be added as well... Good, good. -- Thanks, - Win
From: John Larkin on 31 Jan 2010 19:33 On 31 Jan 2010 16:10:06 -0800, Winfield Hill <Winfield_member(a)newsguy.com> wrote: >John Larkin wrote... >> >> Are you showing the BFT92 as an NPN? Or is it a posting wrap >> artifact? It's a PNP. > > Oops! Good catch, I meant BFR93 for the NPN. Thanks! > >> Packaged transistors with Ft's much above 1 GHz are hard to use... >> they tend to oscillate in any circuit that's not intended to be an >> oscillator. PHEMTs on the other hand usually behave pretty well. > > Even with damping resistors? E.g., EF outputs look > like an inductor, due to the falling beta (assuming > a low source impedance). L = Rs / 2pi fT, above > the breakpoint frequency, f = fT r_e / Rs. That > output inductance resonates with capacitive loads, > but a damping resistor can keep Q = 1 max. Emitter followers, diffamps, cascodes, even plain common-emitter amps like to oscillate with hot transistors, like the zillion-GHz NEC parts for example. By the time you add enough base resistance to calm them down, you may as well have used a slower transistor. The RF boys know how to design tuned circuits that are stable. I've played with fast NPNs, including some 45 GHz SiGe things, as switches. They are disappointingly slow. PHEMTS, on the other hand, switch really, really fast. John
From: John Larkin on 31 Jan 2010 19:40
On 31 Jan 2010 16:26:12 -0800, Winfield Hill <Winfield_member(a)newsguy.com> wrote: >Paul E. Schoen wrote... >> >> >> MPSA06 MMBTA06 PZTA06 MPSA56 MMBTA56 PZTA56 (TO-92 SOT-23 SOT-223) >> MJE180-182 MJE170-172 (TO-225AA) >> 2N3055 MJ2955 (TO-3) >> >> Figured that some power types should be added as well... > > Good, good. Are you going to mention MMICS somewhere else? Some of them make radical wideband amps, even pulse amplifiers, so are options to replace discretes and opamps. They tend to be very stable. John |