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From: Spehro Pefhany on 14 May 2010 10:09 On Fri, 14 May 2010 10:59:21 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >On a sunny day (Thu, 13 May 2010 17:48:41 -0700) it happened John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in ><i37pu594178305v2a62vb99d263og1tfau(a)4ax.com>: > >>I like this as a test: >> >> >> >> +10V >> | >> | >> | >> | >> c >> +5V--------------b >> e >> | >> | >> 1K >> | >> | >> | >> | >> gnd >> >> >>What's the base voltage? >> >>What's the base current? >> >>What's the emitter voltage? >> >>What's the collector current? >> >>What's the collector voltage? >> >>Any other comments? >> >> >>I'm not kidding. One "experienced ee" said that, since the transistor >>is saturated, the collector voltage is zero. A tech applicant said >>that the base voltage is 0.6. >> >>Some people got it right, but nobody has mentioned oscillation so far. >> >>John > >How many asked if it was germanium or Si? >Would be my first question. Could be _both_, or perhaps neither- such as a III-V material (but I'm not sure where to buy the latter in a discrete BJT).
From: Jim Thompson on 14 May 2010 10:30 On Fri, 14 May 2010 06:40:47 GMT, nico(a)puntnl.niks (Nico Coesel) wrote: >John O'Flaherty <quiasmox(a)yeeha.com> wrote: > >>On Thu, 13 May 2010 09:45:57 -0700, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Thu, 13 May 2010 11:02:58 -0500, John O'Flaherty >>><quiasmox(a)yeeha.com> wrote: >>> >>>>I see attenuation of 1/2 at the input, gain of 4 (3+1), and >>>>attenuation of 1/2 at the output. LTSpice agrees, unless I made a >>>>mistake. >>> >>> >>>You did. You left out the pot and the cap. >> >>That wasn't a mistake, it was a choice. I believe the intention of the >>circuit is to have that as an AC ground, that is, as an adjustable >>reference voltage. Is the fact that the capacitor size wasn't >>specified in the published circuit the mistake that you meant to point >>out? > >The capacitor is there to provide an AC ground. The 'DC' (low >frequency) amplification also depends on the potmeter. Video signals >do not have a fixed DC level so you might be in for a bit of trouble >if you use this circuit. Just add the capacitor and some resistors to >mimic the pot and run an AC analyses. > >The circuit would be okay if a second opamp is used to provide a solid >reference voltage. This turns the circuit into a classic non-inverting >summing amplifier hardly worth publishing. Actually this solution will >be smaller since the capacitor would be fairly large anyway. I posted a DC restorer here a while back, AC-coupled input, sync tip clamped to ground. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Jim Thompson on 14 May 2010 10:43 On Fri, 14 May 2010 07:30:46 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Fri, 14 May 2010 06:40:47 GMT, nico(a)puntnl.niks (Nico Coesel) >wrote: > >>John O'Flaherty <quiasmox(a)yeeha.com> wrote: >> >>>On Thu, 13 May 2010 09:45:57 -0700, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>On Thu, 13 May 2010 11:02:58 -0500, John O'Flaherty >>>><quiasmox(a)yeeha.com> wrote: >>>> >>>>>I see attenuation of 1/2 at the input, gain of 4 (3+1), and >>>>>attenuation of 1/2 at the output. LTSpice agrees, unless I made a >>>>>mistake. >>>> >>>> >>>>You did. You left out the pot and the cap. >>> >>>That wasn't a mistake, it was a choice. I believe the intention of the >>>circuit is to have that as an AC ground, that is, as an adjustable >>>reference voltage. Is the fact that the capacitor size wasn't >>>specified in the published circuit the mistake that you meant to point >>>out? >> >>The capacitor is there to provide an AC ground. The 'DC' (low >>frequency) amplification also depends on the potmeter. Video signals >>do not have a fixed DC level so you might be in for a bit of trouble >>if you use this circuit. Just add the capacitor and some resistors to >>mimic the pot and run an AC analyses. >> >>The circuit would be okay if a second opamp is used to provide a solid >>reference voltage. This turns the circuit into a classic non-inverting >>summing amplifier hardly worth publishing. Actually this solution will >>be smaller since the capacitor would be fairly large anyway. > >I posted a DC restorer here a while back, AC-coupled input, sync tip >clamped to ground. > > ...Jim Thompson Here 'tis... http://analog-innovations.com/SED/DC_Restorer_Sync_Separator.pdf ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Michael A. Terrell on 14 May 2010 11:37 Oppie wrote: > > "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message > news:g6bou5ttcqiiugir7eq8gbimd6mjcslrc1(a)4ax.com... > > There are two silly articles in the latest ED, the level shifter and a > > nearly-as-silly Pease Porridge. > > > > John > > So, now ED stands for Electronic Dysfunction? 'Electron Deficiency' ;-) -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: John Larkin on 14 May 2010 11:47
On Fri, 14 May 2010 10:59:21 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >On a sunny day (Thu, 13 May 2010 17:48:41 -0700) it happened John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in ><i37pu594178305v2a62vb99d263og1tfau(a)4ax.com>: > >>I like this as a test: >> >> >> >> +10V >> | >> | >> | >> | >> c >> +5V--------------b >> e >> | >> | >> 1K >> | >> | >> | >> | >> gnd >> >> >>What's the base voltage? >> >>What's the base current? >> >>What's the emitter voltage? >> >>What's the collector current? >> >>What's the collector voltage? >> >>Any other comments? >> >> >>I'm not kidding. One "experienced ee" said that, since the transistor >>is saturated, the collector voltage is zero. A tech applicant said >>that the base voltage is 0.6. >> >>Some people got it right, but nobody has mentioned oscillation so far. >> >>John > >How many asked if it was germanium or Si? >Would be my first question. An interviewee could certainly ask questions, or mention assumptions. Can you still buy germanium transistors? Would that affect many of the answers much? John |