On Friday, October 11, 2013 2:36:13 PM UTC-4, Jim Thompson wrote:> On Wed, 9 Oct 2013 19:51:30 +0000 (UTC), "Rich K." > > <Mungedto@nowhere.cc> wrote: > > > > >Why do you think the op. used this topology over the simple circuit 1 >example? I thank you for your opinions in advance. > > > > >Attached: LTSpice file. > > > > >------------------------------------------------------------------------ > >Version 4 > > >SHEET 1 880 680 > > >WIRE 176 -384 48 -384 > > > > [snip, full listing at Message-ID: <l34c42$ihl$1@dont-email.me>] > > > > >TEXT 368 -88 Left 2 ;The designer used this in a 100kz amp. > > >TEXT 368 -32 Left 2 ;The orignal op amps were TL084's > > Getting back to actually looking at it, I'm not sure if it does > _anything_ at all.I cut out the cap's and then pushed the freq up around 1MHz or so and it showed the some Bandwidth improvement. (But I didn't check any numbers... just played.) George H.> > > > I'll write-out the full-up loop equations and see for sure when I have > > a free moment ;-) > > > > ...Jim Thompson > > -- > > | James E.Thompson | mens | > > | Analog Innovations | et | > > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > > | San Tan Valley, AZ 85142 Skype: Contacts Only | | > > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > > > I love to cook with wine. Sometimes I even put it in the food.
Odd Circuit, OP Amp over OP Amp
Started by ●October 9, 2013
Reply by ●October 11, 20132013-10-11
Reply by ●October 11, 20132013-10-11
On Fri, 11 Oct 2013 12:16:26 -0700 (PDT), George Herold <gherold@teachspin.com> wrote:>On Friday, October 11, 2013 2:36:13 PM UTC-4, Jim Thompson wrote: >> On Wed, 9 Oct 2013 19:51:30 +0000 (UTC), "Rich K." >> >> <Mungedto@nowhere.cc> wrote: >> >> >> >> >Why do you think the op. used this topology over the simple circuit 1 >>example? I thank you for your opinions in advance. >> >> > >> >Attached: LTSpice file. >> > >> >> >------------------------------------------------------------------------ >> >Version 4 >> >> >SHEET 1 880 680 >> >> >WIRE 176 -384 48 -384 >> >> >> >> [snip, full listing at Message-ID: <l34c42$ihl$1@dont-email.me>] >> >> >> >> >TEXT 368 -88 Left 2 ;The designer used this in a 100kz amp. >> >> >TEXT 368 -32 Left 2 ;The orignal op amps were TL084's >> >> Getting back to actually looking at it, I'm not sure if it does >> _anything_ at all. > >I cut out the cap's and then pushed the freq up around 1MHz or so and it showed the some Bandwidth improvement. (But I didn't check any numbers... just played.) > >George H. >> >> >> >> I'll write-out the full-up loop equations and see for sure when I have >> >> a free moment ;-) >> >> >> >> ...Jim Thompson >> >> -- >> >> | James E.Thompson | mens | >> >> | Analog Innovations | et | >> >> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | >> >> | San Tan Valley, AZ 85142 Skype: Contacts Only | | >> >> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | >> >> | E-mail Icon at http://www.analog-innovations.com | 1962 | >> >> >> >> I love to cook with wine. Sometimes I even put it in the food.Goo idea! Easy to implement with my LoopGain checker macro. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●October 11, 20132013-10-11
Always found it strange that there have been so many chips in DIP14 (and SO-14 and others since) with scads of N/C pins. uA723, LM319, even a MCP4922 DAC I'm playing with. They'd fit quite nicely in 10 pin packages, but no one ever invested in that, DIPs have always gone 4, 6, 8, 14, 16, ... I have seen MSOP and DFN styles with nontraditional pin counts. I guess miniaturization is finally forcing frugal pin counts on such things. Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com "Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in message news:sjfg595javrr6tsfj3pcet3445fjfdlb7l@4ax.com...> On Fri, 11 Oct 2013 18:42:12 +0100, John Devereux > <john@devereux.me.uk> wrote: > >>jurb6006@gmail.com writes: >> >>>>"if you are >>> using a quad, so you can easily get a complex zero as well. " >>> >>> I wonder why there are so few with three, or five in the package. Why >>> not seven ? >> >>Is it something to do with common centroid design? > > Pin count and package size. > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | San Tan Valley, AZ 85142 Skype: Contacts Only | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > I love to cook with wine. Sometimes I even put it in the food.
Reply by ●October 12, 20132013-10-12
On Wed, 09 Oct 2013 16:43:39 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Wed, 9 Oct 2013 19:51:30 +0000 (UTC), "Rich K." ><Mungedto@nowhere.cc> wrote: > >>Why do you think the op. used this topology over the simple circuit 1 >>example? I thank you for your opinions in advance. >> >>Attached: LTSpice file. >> >>------------------------------------------------------------------------ >>Version 4 >>SHEET 1 880 680 >[snip] >>TEXT 368 -88 Left 2 ;The designer used this in a 100kz amp. >>TEXT 368 -32 Left 2 ;The orignal op amps were TL084's > >It may be just a scheme to improve _net_ loop-gain-bandwidth-product. > >I have a paper somewhere on such multi-OpAmp schemes. I'll post when >I find it. > > ...Jim ThompsonSimulation of circuit (using original TL084 specifications) yields strange results... 3.5dB peaking at 239KHz, then roll-off normally Phase flatness extends slightly, then is exactly 45� at the frequency peak, then returns to follow same curve as a single OpAmp implementation does. I have no clue what originator was trying to accomplish. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
