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G. K.
Here is another choice, ? Vcbo =-120V, Ccbo ~ 2-3 pF, Ft ~ 100MHz. (Mouser 7 cents each!) -?George From: David
To: TekScopes@... Sent: Tuesday, October 9, 2012 7:23 PM Subject: Re: [TekScopes] Re: Bright dots at start of the trace on a 547
?
Both of the ones I listed are available from Mouser. The 2N5401 and
2N6520 both have a Cob of 6.0pF maximum at 10 and 20 volts respectively but Cobo falls with Vcb so at 60 volts it will be significantly lower. From the graph of Cob versus voltage, it looks like they both could easily be 2.5pF at 60 volts. On Tue, 9 Oct 2012 17:17:25 -0700, David Wise <mailto:david_wise%40phoenix.com> wrote: >MPSA92 is the only through-hole hit at Mouser, but I think Cob is too high. >A couple of SMT parts are 4pF vs 6. FJX99T, 2SA1312, and 2SA1136. > >Dave Wise > >>-----Original Message----- >>From: mailto:TekScopes%40yahoogroups.com >>[mailto:mailto:TekScopes%40yahoogroups.com] On Behalf Of mailto:larrys%40teamlarry.com >>Sent: Tuesday, October 09, 2012 4:57 PM >>To: mailto:TekScopes%40yahoogroups.com >>Subject: Re: [TekScopes] Re: Bright dots at start of the trace on a 547 >> >>Comp PNP should be MPSA92 / 93 >>-ls- >> >> >>"Tom Jobe" <mailto:tomjobe%40gmail.com> wrote: >>> Hi George, >>> Those NPN transistors are a nice find! >>> Thank you for the link to the datasheet. >>> Is there a PNP version? >>> I think that is what they are looking for. >>> tom jobe... >>> >>> >>> >>> >>> ----- Original Message ----- >>> From: G. K. >>> To: mailto:TekScopes%40yahoogroups.com >>> Sent: Tuesday, October 09, 2012 4:31 PM >>> Subject: Re: [TekScopes] Re: Bright dots at start of the trace on a >>> 547 >>> >>> >>> >>> >>> How about the MPSA42 and 43? >>> >>( ). Both >>> are high voltage and reasonable fast. Mouser has stock, and they are >>> cheap. - George >>> >>> >>> From: David <mailto:davidwhess%40gmail.com> >>> To: mailto:TekScopes%40yahoogroups.com >>> Sent: Tuesday, October 9, 2012 3:27 PM >>> Subject: Re: [TekScopes] Re: Bright dots at start of the trace on a >>> 547 >>> >>> >>> >>> >>> The specifications I found for the 2N2207 were Vceo = 50 volts and >>> Vcbo = 70 volts. When the blanking signal is applied to the emitter >>> and the base driven by a relatively low impedance -0.6 volts, the >>> Vcbo >>> is a better match. >>> >>> But even a Vcbo of 70 volts is not much greater than the -68 volts >>> marked on the schematic. Maybe Tektronix graded them for a higher >>> minimum breakdown voltage. >>> >>> On Tue, 09 Oct 2012 21:31:25 -0000, "Albert" >>> >>> wrote: >>> >>> >No, for 151-063 (= 2N2207) Vceo = 70 V, but even then ... >>> >Albert >>> > >>> >> Hi David, >>> >> >>> >> you say "operating close to its breakdown voltage", then you are >>> joking. >>> >> V_ceo is 50 volts and in the schematics, the difference >>between E >>> and C >>> >> is over 67 volts !! >>> >> They are working "beyond the cliff" ! >>> >> >>> >> Herbert >>> > >> >> >> >>------------------------------------ >> >>Yahoo! Groups Links >> >> >> >> |
