Doesn't look like a mixer to me. The only real coupling between the two BJTs is via the collectors, which doesn't really allow one signal to affect the gain of the other signal (i.e. multiply) unless one of the inputs is so large that it takes both transistors into saturation and back out each cycle of the local oscillator. But if you were doing that, there'd be no need for the emitter degeneration or biasing network. Speaking of that, though - the biasing network looks unnecessarily elaborate. Why is there one common 100k resistor in the two biasing networks, with a bypass cap, and then separate small value resistors with bypass caps? Also, why 2.8V supply? Is there a chance that this is a bad design, such that we cannot see the intent because it doesn't do what was intended (or only does it slightly)? On Thu, Sep 29, 2016 at 7:10 PM, Veronica Merryfield < veronica.merryfield@gmail.com> wrote: > Are both inputs in use at the same time? It might be just a way to have > two inputs be able to generate one output. > > > > On Sep 29, 2016, at 5:30 PM, Van Horn, David backcountryaccess.com> wrote: > > > > It's RF, but these days 550kHz might as well be audio-ish. > > > > I'm just bugged that I haven't found this configuration anywhere in > Horowitz and Hill, Ghausi, or google. > > Not sure what the designer was trying to do. > > > > > > -----Original Message----- > > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On > Behalf Of Richard Prosser > > Sent: Thursday, September 29, 2016 1:35 PM > > To: Microcontroller discussion list - Public. > > Subject: Re: [EE] Long tailed pair, sort of. > > > > Yes, That was my guess. > > It seems to be tuned to about 550kHz depending on strays and the load > charecteristics. Seems a bit strange for an audio application (IIRC). > > Could there be a VLF clock function involved? > > Any idea as to the type & levels of the input signals? > > > > RP > > > > On 30 September 2016 at 02:07, wrote: > >> It looks to me like it is being used as an RF mixer or modulator, > considering the tuned circuit in the collector circuit. > >> > >> A bit rough and crude maybe, but presumably works. > >> > >> > >> > >>> -----Original Message----- > >>> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On > >>> Behalf Of David VanHorn > >>> Sent: 29 September 2016 13:07 > >>> To: Microcontroller discussion list - Public. > >>> Subject: Re: [EE] Long tailed pair, sort of. > >>> > >>> Yes > >>> > >>> On Sep 29, 2016 2:20 AM, "Richard Prosser" > wrote: > >>> > >>>> Hi David, > >>>> Silly question, where is the output. TP18 ??? > >>>> > >>>> RP > >>>> > >>>> On 29 September 2016 at 10:55, Van Horn, David > >>>> wrote: > >>>>> Like this > >>>>> > >>>>> -----Original Message----- > >>>>> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On > >>>> Behalf Of Jason White > >>>>> Sent: Wednesday, September 28, 2016 11:25 AM > >>>>> To: Microcontroller discussion list - Public. > >>>>> Subject: Re: [EE] Long tailed pair, sort of. > >>>>> > >>>>> Just out of curiosity, could you post a schematic? It might help > >>>>> to see > >>>> it in context. > >>>>> > >>>>> On Wed, Sep 28, 2016 at 10:02 AM, Van Horn, David < > >>>>> david.vanhorn@ > >>>> backcountryaccess.com> wrote: > >>>>> > >>>>>> Possible. I googled that and didn't see anything other than > >>>>>> differentials though, with one collector tied high. > >>>>>> It's an odd configuration. > >>>>>> > >>>>>> -----Original Message----- > >>>>>> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] > >>>>>> On Behalf Of Sean Breheny > >>>>>> Sent: Thursday, September 22, 2016 5:44 PM > >>>>>> To: Microcontroller discussion list - Public. > >>>>>> Subject: Re: [EE] Long tailed pair, sort of. > >>>>>> > >>>>>> Could it be a two-input inverting summing amplifier? It is too > >>>>>> symmetrical to be a differential amplifier. > >>>>>> > >>>>>> On Tue, Sep 20, 2016 at 12:27 AM, David VanHorn > >>>>>> > >>>>>> wrote: > >>>>>> > >>>>>>> It's supposed to be a differential amplifier, but I don't > >>>>>>> think it's > >>>>>> right. > >>>>>>> > >>>>>>> On Mon, Sep 19, 2016 at 9:30 PM, Jean-Paul Louis > >>>>>>> > >>>>>> wrote: > >>>>>>> > >>>>>>>> NAND gate using RTL logic? > >>>>>>>> > >>>>>>>> Jean-Paul > >>>>>>>> N1JPL > >>>>>>>> > >>>>>>>> > >>>>>>>>> On Sep 19, 2016, at 6:07 PM, Van Horn, David > >>>>>>>>> >>>>>>>> backcountryaccess.com> wrote: > >>>>>>>>> > >>>>>>>>> I am looking at an amplifier, which is almost a classic > >>>>>>>>> long tailed > >>>>>>> pair > >>>>>>>> as figure 2 here: > >>>>>>>> https://en.wikipedia.org/wiki/Differential_amplifier > >>>>>>>>> > >>>>>>>>> The difference is that there is only one collector > >>>>>>>>> resistor, and both > >>>>>>>> collectors are tied together. > >>>>>>>>> What's up with that? > >>>>>>>>> > >>>>>>>>> I haven't seen that configuration in Horowitz and Hill or Ghaus= i. > >>>>>>>>> > >>>>>>>>> > >>>>>>>>> -- > >>>>>>>>> David VanHorn > >>>>>>>>> Lead Hardware Engineer > >>>>>>>>> > >>>>>>>>> Backcountry Access, Inc. > >>>>>>>>> 2820 Wilderness Pl, Unit H Boulder, CO 80301 USA > >>>>>>>>> phone: 303-417-1345 x110 > >>>>>>>>> email: > >>>>>>>>> david.vanhorn@backcountryaccess.com >>>>>>>> backcountryaccess.com> > >>>>>>>>> > >>>>>>>>> -- > >>>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list > >>>>>>>>> archive View/change your membership options at > >>>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist > >>>>>>>> > >>>>>>>> > >>>>>>>> > >>>>>>>> Just my $0.02, > >>>>>>>> > >>>>>>>> Jean-Paul > >>>>>>>> N1JPL > >>>>>>>> > >>>>>>>> > >>>>>>>> > >>>>>>>> > >>>>>>>> -- > >>>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list > >>>>>>>> archive View/change your membership options at > >>>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist > >>>>>>>> > >>>>>>> -- > >>>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >>>>>>> View/change your membership options at > >>>>>>> http://mailman.mit.edu/mailman/listinfo/piclist > >>>>>>> > >>>>>> -- > >>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >>>>>> View/change your membership options at http://mailman.mit.edu/ > >>>>>> mailman/listinfo/piclist > >>>>>> > >>>>>> -- > >>>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >>>>>> View/change your membership options at > >>>>>> http://mailman.mit.edu/mailman/listinfo/piclist > >>>>>> > >>>>> > >>>>> > >>>>> > >>>>> -- > >>>>> Jason White > >>>>> -- > >>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >>>> View/change your membership options at http://mailman.mit.edu/ > >>>> mailman/listinfo/piclist > >>>>> > >>>>> -- > >>>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >>>>> View/change your membership options at > >>>>> http://mailman.mit.edu/mailman/listinfo/piclist > >>>>> > >>>> -- > >>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >>>> View/change your membership options at > >>>> http://mailman.mit.edu/mailman/listinfo/piclist > >>>> > >>> -- > >>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >>> View/change your membership options at > >>> http://mailman.mit.edu/mailman/listinfo/piclist > >> > >> -- > >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > >> View/change your membership options at > >> http://mailman.mit.edu/mailman/listinfo/piclist > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .