On a sunny day (Thu, 10 Jan 2013 17:31:00 -0800 (PST)) it happened bloggs.fredbloggs.fred@gmail.com wrote in <ba180019-c9c9-4162-a39d-43436007e27f@googlegroups.com>:>> +3.3V >> >> --- >> >> | >> >> .-------+-------. >> >> | | >> >> 5K R1 C1 |/ Q2 >> >> | 100n .------| 2n5089 >> >> +---||-|--. |>. >> >> | | | | >> >> 15k R2 | '-----+------> >> >> | | | >> >> C2 +------' R3 820R >> >> 10n |/ Q1 | >> >> >--||-+--| 2n5089 .------+ >> >> | |>. | | >> >> | | | R4 470R >> >> | === | | >> >> | | === >> >> '-----R5------' >> >> 220kmm, an ASCII magnifier?
Cute amplifier - bootstrapped
Started by ●January 10, 2013
Reply by ●January 11, 20132013-01-11
Reply by ●January 11, 20132013-01-11
On Thu, 10 Jan 2013 21:31:51 -0800 (PST), bloggs.fredbloggs.fred@gmail.com wrote:>On Thursday, January 10, 2013 9:45:33 PM UTC-5, John Larkin wrote: > >> >> Not to thread-drift or anything (who, me?) but similar toplogies are, if >> >> possible, even more ancient than JT. This is the once-famous "GE circuit", >> >> widely used for phono and tape preamps. >> >> >> >> https://dl.dropbox.com/u/53724080/Circuits/GEcircuit.jpg >> >> >> > >That's not even remotely close. That is the two transistor job with superstablized Q-point self-bias and series feedback.Gosh, really? -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●January 11, 20132013-01-11
On Fri, 11 Jan 2013 09:26:51 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:>On a sunny day (Thu, 10 Jan 2013 17:31:00 -0800 (PST)) it happened >bloggs.fredbloggs.fred@gmail.com wrote in ><ba180019-c9c9-4162-a39d-43436007e27f@googlegroups.com>: > >>> +3.3V >>> >>> --- >>> >>> | >>> >>> .-------+-------. >>> >>> | | >>> >>> 5K R1 C1 |/ Q2 >>> >>> | 100n .------| 2n5089 >>> >>> +---||-|--. |>. >>> >>> | | | | >>> >>> 15k R2 | '-----+------> >>> >>> | | | >>> >>> C2 +------' R3 820R >>> >>> 10n |/ Q1 | >>> >>> >--||-+--| 2n5089 .------+ >>> >>> | |>. | | >>> >>> | | | R4 470R >>> >>> | === | | >>> >>> | | === >>> >>> '-----R5------' >>> >>> 220k > >mm, an ASCII magnifier?Just ASL each byte. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●January 11, 20132013-01-11
On Friday, January 11, 2013 6:30:26 AM UTC-5, John Larkin wrote:> >> https://dl.dropbox.com/u/53724080/Circuits/GEcircuit.jpg> Gosh, really? >Yep- really- and that circuit has come up as a topic before. You couldn't get to square one figuring out the DC bias then IIRC.
Reply by ●January 11, 20132013-01-11
On 01/10/2013 08:49 PM, bloggs.fredbloggs.fred@gmail.com wrote:> On Thursday, January 10, 2013 8:44:27 PM UTC-5, Phil Hobbs wrote: > >> You can bootstrap a follower, in fact you have to if you want the >> >> bootstrap itself to work properly, but that involves doing something >> >> with its collector. >> > > Huh? You bootstrap the follower to increase its input impedance, not lower its output impedance. > >The emitter bootstraps itself, if you use a current source load. (*) It's the collector of the follower that you have to bootstrap, to get rid of the Early effect and C_CB. Cheers Phil Hobbs (*) Sprinkling simulated inductors made out of BFP640s is good medicine to stiffen current sources at high frequency. Cap from base to emitter (with a bead to keep it stable) and a resistor from base to collector. -- 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 11, 20132013-01-11
On Fri, 11 Jan 2013 06:55:02 -0800 (PST), bloggs.fredbloggs.fred@gmail.com wrote:>On Friday, January 11, 2013 6:30:26 AM UTC-5, John Larkin wrote: > >> >> https://dl.dropbox.com/u/53724080/Circuits/GEcircuit.jpg > >> Gosh, really? >> > >Yep- really- and that circuit has come up as a topic before. You couldn't get to square one figuring out the DC bias then IIRC.Thanks for not confusing us with any facts or schematics. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●January 11, 20132013-01-11
On 01/10/2013 09:03 PM, dagmargoodboat@yahoo.com wrote:> On Jan 10, 8:08 pm, John Larkin<jlar...@highlandtechnology.com> > wrote: >> On Thu, 10 Jan 2013 16:34:26 -0800 (PST), dagmargoodb...@yahoo.com >> wrote: >> >> >> >> >> >> >> >> >> >>> Adapted from something I saw on the web... >> >>> I had to scratch my head until I understood C1: it bootstraps Q1's >>> collector load (R2) impedance, turning it effectively into a current >>> source. Gain is accordingly greatly increased. G = ~220 @ 40KHz. >> >>> +3.3V >>> --- >>> | >>> .-------+-------. >>> | | >>> 5K R1 C1 |/ Q2 >>> | 100n .------| 2n5089 >>> +---||-|--. |>. >>> | | | | >>> 15k R2 | '-----+------> >>> | | | >>> C2 +------' R3 820R >>> 10n |/ Q1 | >>>> --||-+--| 2n5089 .------+ >>> | |>. | | >>> | | | R4 470R >>> | === | | >>> | | === >>> '-----R5------' >>> 220k >> >>> R3-R4 set the d.c. output level. >> >>> Gain is component-sensitive, but the bootstrap is a cute technique. >>> That with feedback could stabilize the gain. >> >> Bootstrapping rocks. This thing improves the constant-current-ness of >> a linear ramp generator at higher speeds.... >> >> https://dl.dropbox.com/u/53724080/Circuits/Current_Sources/Isrc_5.JPG > > I remember that trick of yours. Fun. > >> Phil does some uber-bootstrapped stuff with jfet front ends. He sort >> of bootstraps the entire planet, or the entire universe, all around a >> BF862. > > One of the neatest I've seen was a VLF JFET amplifier. It used > transformers to bootstrap its input capacitance to nada. > > JamesYou can combine that with noise resistance matching too, which is a huge win. 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 11, 20132013-01-11
On 01/10/2013 09:03 PM, John Larkin wrote:> On Thu, 10 Jan 2013 20:44:27 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 1/10/2013 8:31 PM, bloggs.fredbloggs.fred@gmail.com wrote: >>> On Thursday, January 10, 2013 7:34:26 PM UTC-5, dagmarg...@yahoo.com wrote: >>>> Adapted from something I saw on the web... >>>> >>>> >>>> >>>> I had to scratch my head until I understood C1: it bootstraps Q1's >>>> >>>> collector load (R2) impedance, turning it effectively into a current >>>> >>>> source. Gain is accordingly greatly increased. G = ~220 @ 40KHz. >>>> >>>> >>>> >>>> +3.3V >>>> >>>> --- >>>> >>>> | >>>> >>>> .-------+-------. >>>> >>>> | | >>>> >>>> 5K R1 C1 |/ Q2 >>>> >>>> | 100n .------| 2n5089 >>>> >>>> +---||-|--. |>. >>>> >>>> | | | | >>>> >>>> 15k R2 | '-----+------> >>>> >>>> | | | >>>> >>>> C2 +------' R3 820R >>>> >>>> 10n |/ Q1 | >>>> >>>>> --||-+--| 2n5089 .------+ >>>> >>>> | |>. | | >>>> >>>> | | | R4 470R >>>> >>>> | === | | >>>> >>>> | | === >>>> >>>> '-----R5------' >>>> >>>> 220k >>>> >>>> >>>> >>>> R3-R4 set the d.c. output level. >>>> >>>> >>>> >>>> Gain is component-sensitive, but the bootstrap is a cute technique. >>>> >>>> That with feedback could stabilize the gain. >>>> >>>> Cheers, >>>> >>>> James Arthur >>> >>> You need to turn that around, it is the emitter follower that is being bootstrapped and not the CE. So the CE + CC composite looks like the classic very high gain single pole amplifier inside the feedback loop formed by the resistor shunt feedback divider, everything is simplified. See the textbook write-up here, section 1.17.2: >>> http://books.google.com/books?id=1-jiL0s8y7EC&pg=PA78&lpg=PA78&dq=bootstrapped+emitter+follower&source=bl&ots=Vm7TxTwrbA&sig=qs8fZulqYscWBdVuO8TND8jDqI8&hl=en&sa=X&ei=OmnvUMihJ4n49gSmyIHQAw&sqi=2&ved=0CC4Q6AEwAA#v=onepage&q=bootstrapped%20emitter%20follower&f=false >>> >> >> The output impedance of the follower is probably a few tens of ohms. >> For small signals it doesn't even notice the extra loading on its emitter. >> >> You can bootstrap a follower, in fact you have to if you want the >> bootstrap itself to work properly, but that involves doing something >> with its collector. >> >> Cheers >> >> Phil Hobbs > > We bootstrapped a unity-gain 5-volt chopamp to let it follow +-40 volt > swings. That was a bear to get working correctly and reliably. The > PSRR of the amp was negative (ie, it had gain from power rail to > output) at some frequencies. > >Blech. That's why they quote PSRR as an equivalent input voltage, of course. 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 11, 20132013-01-11
On Friday, January 11, 2013 10:46:59 AM UTC-5, John Larkin wrote:> > > Thanks for not confusing us with any facts or schematics. > >You're very welcome.
Reply by ●January 11, 20132013-01-11
On Thu, 10 Jan 2013 18:03:28 -0800 (PST), dagmargoodboat@yahoo.com wrote:>On Jan 10, 8:08�pm, John Larkin <jlar...@highlandtechnology.com> >wrote: >> On Thu, 10 Jan 2013 16:34:26 -0800 (PST), dagmargoodb...@yahoo.com >> wrote: >> >> >> >> >> >> >> >> >> >> >Adapted from something I saw on the web... >> >> >I had to scratch my head until I understood C1: it bootstraps Q1's >> >collector load (R2) impedance, turning it effectively into a current >> >source. �Gain is accordingly greatly increased. G = ~220 @ 40KHz. >> >> > � � � � � � � � +3.3V >> > � � � � � � � � �--- >> > � � � � � � � � � | >> > � � � � � .-------+-------. >> > � � � � � | � � � � � � � | >> > � � � 5K R1 �C1 � � � � |/ �Q2 >> > � � � � � | 100n .------| �2n5089 >> > � � � � � +---||-|--. � |>. >> > � � � � � | � � �| �| � � | >> > � � �15k R2 � � �| �'-----+------> >> > � � � � � | � � �| � � � �| >> > � C2 � � �+------' � � � R3 820R >> > � 10n � |/ Q1 � � � � � � | >> >>--||-+--| �2n5089 �.------+ >> > � � �| �|>. � � � �| � � �| >> > � � �| � �| � � � �| � � R4 470R >> > � � �| � === � � � | � � �| >> > � � �| � � � � � � | � � === >> > � � �'-----R5------' >> > � � � � � 220k >> >> >R3-R4 set the d.c. output level. >> >> >Gain is component-sensitive, but the bootstrap is a cute technique. >> >That with feedback could stabilize the gain. >> >> Bootstrapping rocks. This thing improves the constant-current-ness of >> a linear ramp generator at higher speeds.... >> >> https://dl.dropbox.com/u/53724080/Circuits/Current_Sources/Isrc_5.JPG > >I remember that trick of yours. Fun. > >> Phil does some uber-bootstrapped stuff with jfet front ends. He sort >> of bootstraps the entire planet, or the entire universe, all around a >> BF862. > >One of the neatest I've seen was a VLF JFET amplifier. It used >transformers to bootstrap its input capacitance to nada. > >JamesAlso google "noiseless feedback amplifier" -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
