"Phil Hobbs" wrote in message news:e7idnT39aqK_9TPLnZ2dnUU7-a2dnZ2d@supernews.com...>> Do I have to do all the impedande/admittance matrix inversions >> myself, or write my own software? If the required data is even >> available? > >It isn't difficult--probably 50 lines of Matlab that you can use over and >over. Suck it up. >Or if you're a cheap SOB, too... :-) GNU Octave. Not quite as powerful as MATLAB, but the core functionality, and much of what you'd do with it, is all there. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Cascode substitutions
Started by ●January 31, 2016
Reply by ●January 31, 20162016-01-31
Reply by ●January 31, 20162016-01-31
Den s�ndag den 31. januar 2016 kl. 21.24.02 UTC+1 skrev Tim Williams:> "Phil Hobbs" wrote in message > news:e7idnT39aqK_9TPLnZ2dnUU7-a2dnZ2d@supernews.com... > >> Do I have to do all the impedande/admittance matrix inversions > >> myself, or write my own software? If the required data is even > >> available? > > > >It isn't difficult--probably 50 lines of Matlab that you can use over and > >over. Suck it up. > > > > Or if you're a cheap SOB, too... :-) GNU Octave. Not quite as powerful > as MATLAB, but the core functionality, and much of what you'd do with it, > is all there.afaict the biggest difference between matlab and octave is the more fancy plotting and gui stuff in matlab -Lasse
Reply by ●January 31, 20162016-01-31
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> Wrote in message:> On 01/31/2016 02:36 PM, bitrex wrote: >> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> Wrote in message: >>> On 01/31/2016 12:26 PM, bitrex wrote: >>>> John Larkin <jjlarkin@highlandtechnology.com> Wrote in message: >>>>> On Sun, 31 Jan 2016 05:34:23 -0600, "Tim Williams" >>>>> <tiwill@seventransistorlabs.com> wrote: >>>>> >>>>>> Designing an RF amplifier. Concept is, high power, complementary cascodes >>>>>> for the output stage (with heavy class A use, but being PP, class AB is an >>>>>> option). 50 ohm output, direct drive, say 10W level. >>>>>> >>>>>> I happen to have a complementary pair that's not too slow (2SC2690A and >>>>>> 2SA1220A), and I'd like to maximize the bandwidth around that. The NPN >>>>>> side is fine, I have a 30V, 1A, 2GHz transistor that would pair very well >>>>>> with it. Don't have any such thing for the PNP side. >>>>>> >>>>>> So, what if I fake a PNP, by wrapping, say, a BFT92 around the NPN? >>>>>> http://seventransistorlabs.com/Images/Sziklai_Cascode.png >>>>>> That'd be Q1 = BFT92, Q2 = 2SC4821, Q3 = 2SA1220A, and resistors for >>>>>> flavor, but probably roughly representative. (Ground wouldn't actually be >>>>>> ground-ground, but probably something like +40V, and "+12V" would be >>>>>> +45V.) >>>>>> >>>>>> The combination is still fast... ah, but Sziklai connections have a >>>>>> propensity for oscillation all their own, let alone in a cascode, plus >>>>>> whatever other machinations I might have for feedback around the thing. >>>>>> Game killer? >>>>>> >>>>>> The other option would be folded cascode, which is understandably rather >>>>>> wasteful for a power stage! >>>>>> >>>>>> Tim >>>>> >>>>> What's the frequency and the bandwidth requirement? >>>>> >>>>> Regular low-frequency circuit topologies generally don't scale well >>>>> into RF amps. >>>>> >>>> >>>> >>>> Does anyone use that admittance/Z parameter matrix stuff for RF >>>> amp design/stability analysis that I've read about in books like >>>> "Intro to RF Design" by Wes Hayward, or do they just mess with it >>>> in Spice and are then like "eh works well enough ship >>>> it" >>>> >>>> It seems difficult to even find device data sheets that have those >>>> parameters evaluated at enough data points to be useful (so if >>>> you don't have a 20k network analyzer to check it yourself at the >>>> frequency of interest you're SOL), and I once searched for >>>> software that could deal with such things that didn't cost 5k and >>>> I couldn't really find much. >>>> >>> >>> The classical approach has the great virtue that it tells you how well >>> you _can_ do, so you don't wind up attempting recreational >>> impossibilities on the one hand, or turning a silk purse back into a >>> sow's ear on the other. >>> >>> Cheers >>> >>> Phil "Do the math" Hobbs >>> >> >> That approach cetainly is appealing, but it seems like there often >> just aren't the tools available to do it. >> >> Do I have to do all the impedande/admittance matrix inversions >> myself, or write my own software? If the required data is even >> available? > > It isn't difficult--probably 50 lines of Matlab that you can use over > and over. Suck it up.Probably SciPy, I'm not big on Matlab. I've got Python skills anyway. Array indices starting at 1 does not compute>> This is 2k16, come on! I have Angry Birds waiting on me... > > You've already said that you're a moral relativist, so there's no use > appealing to your better nature. ;)True, but it doesn't seem to stop people from trying...> Cheers > > Phil Hobbs >-- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
Reply by ●January 31, 20162016-01-31
"John Larkin" wrote in message news:79bsabhfcqnegk82mtt708to85n21jbadg@4ax.com...> What's the frequency and the bandwidth requirement? > > Regular low-frequency circuit topologies generally don't scale well > into RF amps.At least 100MHz, prefer "as much as possible". Without going out of my way for, like, PHEMTs and shit I mean. ;-) Gain at least 20dB, but that can be spread over several stages, and anyway, 1W input is pretty easily solved with a handful of other things (a 2N3866 would do that handily). Some other junkbox items include video output transistors (something like 100V 200mA, fT's from 200MHz to ~1.2GHz), with the downside that I'll need to parallel several to achieve full output power. Parallel may be an advantage. I can use smaller 'input' side transistors for individual cascodes, and just wire all their outputs in parallel. Maybe even with some phase shift to get a distributed amplifier going. Transformer coupling is okay, and I may just do so, to solve the PNP problem (and to keep R_L in the sweet spot for whatever transistors I've grabbed). In that case, LF limit is <= 100kHz, which should be easily enough handled by a little wire on a pot core or something. I'm not worried about that. Also tempted to play with some of those SuperJunction MOSFETs I have on hand. 600V 5A and ~10pF above 50V is fun. They are apparently free from 2nd breakdown, too. Downsides are the relatively low dissipation for the ratings, and the still rather massive Ciss making them hard to drive (like, you'd need a magnified cascode to do it). This will be nothing like a "regular low-frequency circuit"; feedback will be local. Especially if I'm doing something distributed... the phase shift can be expected to be several cycles by cutoff. No GNFB reasonable there. I'm also assuming a 50 ohm load (with whatever matching as needed), so I don't much care about Zo. I suppose the ideal solution would use a mix of local NFB to get an active 50 ohms Zo (until cutoff, where the peaking coils take over), but that's optional. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●January 31, 20162016-01-31
On 1/31/2016 3:28 PM, Lasse Langwadt Christensen wrote:> Den s�ndag den 31. januar 2016 kl. 21.24.02 UTC+1 skrev Tim Williams: >> "Phil Hobbs" wrote in message >> news:e7idnT39aqK_9TPLnZ2dnUU7-a2dnZ2d@supernews.com... >>>> Do I have to do all the impedande/admittance matrix inversions >>>> myself, or write my own software? If the required data is even >>>> available? >>> >>> It isn't difficult--probably 50 lines of Matlab that you can use over and >>> over. Suck it up. >>> >> >> Or if you're a cheap SOB, too... :-) GNU Octave. Not quite as powerful >> as MATLAB, but the core functionality, and much of what you'd do with it, >> is all there. > > afaict the biggest difference between matlab and octave is the more > fancy plotting and gui stuff in matlabMatlab has a lot of wizards and help facilities built in. With octave you end up typing lookfor a lot and then hunting for more information or worked examples to figure out how to make something happen. The latest release of Octave (4.0.0) is quite usable and does come with a GUI/IDE that makes life a lot easier. -- Grizzly H.
Reply by ●January 31, 20162016-01-31
mixed nuts <melopsitticus@undulatus.budgie> Wrote in message:> On 1/31/2016 12:26 PM, bitrex wrote: >> John Larkin <jjlarkin@highlandtechnology.com> Wrote in message: >>> On Sun, 31 Jan 2016 05:34:23 -0600, "Tim Williams" >>> <tiwill@seventransistorlabs.com> wrote: >>> >>>> Designing an RF amplifier. Concept is, high power, complementary cascodes >>>> for the output stage (with heavy class A use, but being PP, class AB is an >>>> option). 50 ohm output, direct drive, say 10W level. >>>> >>>> I happen to have a complementary pair that's not too slow (2SC2690A and >>>> 2SA1220A), and I'd like to maximize the bandwidth around that. The NPN >>>> side is fine, I have a 30V, 1A, 2GHz transistor that would pair very well >>>> with it. Don't have any such thing for the PNP side. >>>> >>>> So, what if I fake a PNP, by wrapping, say, a BFT92 around the NPN? >>>> http://seventransistorlabs.com/Images/Sziklai_Cascode.png >>>> That'd be Q1 = BFT92, Q2 = 2SC4821, Q3 = 2SA1220A, and resistors for >>>> flavor, but probably roughly representative. (Ground wouldn't actually be >>>> ground-ground, but probably something like +40V, and "+12V" would be >>>> +45V.) >>>> >>>> The combination is still fast... ah, but Sziklai connections have a >>>> propensity for oscillation all their own, let alone in a cascode, plus >>>> whatever other machinations I might have for feedback around the thing. >>>> Game killer? >>>> >>>> The other option would be folded cascode, which is understandably rather >>>> wasteful for a power stage! >>>> >>>> Tim >>> >>> What's the frequency and the bandwidth requirement? >>> >>> Regular low-frequency circuit topologies generally don't scale well >>> into RF amps. >>> >> >> Does anyone use that admittance/Z parameter matrix stuff for RF >> amp design/stability analysis that I've read about in books like >> "Intro to RF Design" by Wes Hayward, or do they just mess with it >> in Spice and are then like "eh works well enough ship >> it" > > Not so much anymore - it's all wired into RF design packages - some > bloody expensive, a couple free. SPICE input files can be used - if you > have a well characterized SPICE model, the simulation engine will > understand it. S-Parameter simulations are the norm. Generally, these > packages will work with MATLAB/Octave, VHDL, Verilog... or have > something similar built in - lots of post processing and modeling options. > > SPICE sucks for modeling transmission lines. The RF/Microwave packages > will work directly with dimensions and materials - just plug in the > numbers or click on a library definition. Life is good. > > Optimizers are generally available - select the free parameters, set up > goals and constraints, go for coffee. Bandpass, gain, linearity, noise > figure... can be optimized and often a layout is only a few clicks away. >Interesting - do you know what particular nonlinear optimizer algorithm they're using for such things?> >> >> It seems difficult to even find device data sheets that have those >> parameters evaluated at enough data points to be useful (so if >> you don't have a 20k network analyzer to check it yourself at the >> frequency of interest you're SOL), and I once searched for >> software that could deal with such things that didn't cost 5k and >> I couldn't really find much. > > Look at QUCS - GPLed Design package if you want to get your feet wet. > No layout capability but otherwise very functional. SPICE models can be > added but the usual issues encountered with SPICE variants apply - > PSPICE is not the same as the SPICE 3 derivatives, encrypted stuff isn't > supported, you'll sometimes have to go through converting a netlist to a > subcircuit schematic to get an opamp to work right etc. > > https://en.wikipedia.org/wiki/Quite_Universal_Circuit_Simulator > http://qucs.sourceforge.net/ > > If you decide to try it, install Octave (4.0.0 is current) first. > > The windows port works but has some annoying issues that are probably > related to specific device drivers - print formatting, display quirks, > access rights etc. If you use Linux, there are tested binaries in the > repositories for most distros which are generally very clean. > > -- > Grizzly H. >Thanks, I'll check it out. I ain't run Windows on anything around here. Well, at least not on anything important. -- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
Reply by ●January 31, 20162016-01-31
"Tim Williams" <tiwill@seventransistorlabs.com> Wrote in message:> "John Larkin" wrote in message > news:79bsabhfcqnegk82mtt708to85n21jbadg@4ax.com... >> What's the frequency and the bandwidth requirement? >> >> Regular low-frequency circuit topologies generally don't scale well >> into RF amps. > > > At least 100MHz, prefer "as much as possible". Without going out of my > way for, like, PHEMTs and shit I mean. ;-)GaSFETs? -- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
Reply by ●January 31, 20162016-01-31
On 1/31/2016 3:48 PM, bitrex wrote:> mixed nuts <melopsitticus@undulatus.budgie> Wrote in message:[...]>> >> Optimizers are generally available - select the free parameters, set up >> goals and constraints, go for coffee. Bandpass, gain, linearity, noise >> figure... can be optimized and often a layout is only a few clicks away. >> > > Interesting - do you know what particular nonlinear optimizer > algorithm they're using for such things?That varies, sometimes in magical ways. There's always a Monte Carlo option. There have been simulated annealing methods in use but I haven't seen that mentioned for a while. Sometimes there are direct synthesis methods available for things like matching networks. This one is GPLed and uses a parallel differential evolution method (works with QUCS and LTSpice): http://asco.sourceforge.net/ -- Grizzly H.
Reply by ●January 31, 20162016-01-31
On 01/31/2016 03:42 PM, bitrex wrote:>> >> You've already said that you're a moral relativist, so there's no use >> appealing to your better nature. ;) > > True, but it doesn't seem to stop people from trying...A lot of moral relativists are much better than their principles, and I hope you're one. The principles themselves are so bad that it's scarcely possible for someone to be worse. I try very hard to deal only with straight shooters. I've had to fire customers who weren't, and I certainly wouldn't knowingly work with someone whose moral ideas were controlled by his own convenience. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●January 31, 20162016-01-31
On Sun, 31 Jan 2016 14:58:48 -0500, mixed nuts <melopsitticus@undulatus.budgie> wrote:>On 1/31/2016 12:26 PM, bitrex wrote: >> John Larkin <jjlarkin@highlandtechnology.com> Wrote in message: >>> On Sun, 31 Jan 2016 05:34:23 -0600, "Tim Williams" >>> <tiwill@seventransistorlabs.com> wrote: >>> >>>> Designing an RF amplifier. Concept is, high power, complementary cascodes >>>> for the output stage (with heavy class A use, but being PP, class AB is an >>>> option). 50 ohm output, direct drive, say 10W level. >>>> >>>> I happen to have a complementary pair that's not too slow (2SC2690A and >>>> 2SA1220A), and I'd like to maximize the bandwidth around that. The NPN >>>> side is fine, I have a 30V, 1A, 2GHz transistor that would pair very well >>>> with it. Don't have any such thing for the PNP side. >>>> >>>> So, what if I fake a PNP, by wrapping, say, a BFT92 around the NPN? >>>> http://seventransistorlabs.com/Images/Sziklai_Cascode.png >>>> That'd be Q1 = BFT92, Q2 = 2SC4821, Q3 = 2SA1220A, and resistors for >>>> flavor, but probably roughly representative. (Ground wouldn't actually be >>>> ground-ground, but probably something like +40V, and "+12V" would be >>>> +45V.) >>>> >>>> The combination is still fast... ah, but Sziklai connections have a >>>> propensity for oscillation all their own, let alone in a cascode, plus >>>> whatever other machinations I might have for feedback around the thing. >>>> Game killer? >>>> >>>> The other option would be folded cascode, which is understandably rather >>>> wasteful for a power stage! >>>> >>>> Tim >>> >>> What's the frequency and the bandwidth requirement? >>> >>> Regular low-frequency circuit topologies generally don't scale well >>> into RF amps. >>> >> >> Does anyone use that admittance/Z parameter matrix stuff for RF >> amp design/stability analysis that I've read about in books like >> "Intro to RF Design" by Wes Hayward, or do they just mess with it >> in Spice and are then like "eh works well enough ship >> it" > >Not so much anymore - it's all wired into RF design packages - some >bloody expensive, a couple free. SPICE input files can be used - if you >have a well characterized SPICE model, the simulation engine will >understand it. S-Parameter simulations are the norm. Generally, these >packages will work with MATLAB/Octave, VHDL, Verilog... or have >something similar built in - lots of post processing and modeling options. > >SPICE sucks for modeling transmission lines. The RF/Microwave packages >will work directly with dimensions and materials - just plug in the >numbers or click on a library definition. Life is good.Think so? I Spice txlines all the time, and the results seem to be realistic. -- John Larkin Highland Technology, Inc lunatic fringe electronics
