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Cute amplifier - bootstrapped

Started by Unknown January 10, 2013
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?
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
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
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.
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
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
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. > > James
You 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
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
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.
On Thu, 10 Jan 2013 18:03:28 -0800 (PST), dagmargoodboat@yahoo.com wrote:

>On Jan 10, 8:08&#2013266080;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. &#2013266080;Gain is accordingly greatly increased. G = ~220 @ 40KHz. >> >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; +3.3V >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080;--- >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; .-------+-------. >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | >> > &#2013266080; &#2013266080; &#2013266080; 5K R1 &#2013266080;C1 &#2013266080; &#2013266080; &#2013266080; &#2013266080; |/ &#2013266080;Q2 >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | 100n .------| &#2013266080;2n5089 >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; +---||-|--. &#2013266080; |>. >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; &#2013266080;| &#2013266080;| &#2013266080; &#2013266080; | >> > &#2013266080; &#2013266080; &#2013266080;15k R2 &#2013266080; &#2013266080; &#2013266080;| &#2013266080;'-----+------> >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; &#2013266080;| &#2013266080; &#2013266080; &#2013266080; &#2013266080;| >> > &#2013266080; C2 &#2013266080; &#2013266080; &#2013266080;+------' &#2013266080; &#2013266080; &#2013266080; R3 820R >> > &#2013266080; 10n &#2013266080; |/ Q1 &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | >> >>--||-+--| &#2013266080;2n5089 &#2013266080;.------+ >> > &#2013266080; &#2013266080; &#2013266080;| &#2013266080;|>. &#2013266080; &#2013266080; &#2013266080; &#2013266080;| &#2013266080; &#2013266080; &#2013266080;| >> > &#2013266080; &#2013266080; &#2013266080;| &#2013266080; &#2013266080;| &#2013266080; &#2013266080; &#2013266080; &#2013266080;| &#2013266080; &#2013266080; R4 470R >> > &#2013266080; &#2013266080; &#2013266080;| &#2013266080; === &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; &#2013266080;| >> > &#2013266080; &#2013266080; &#2013266080;| &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; | &#2013266080; &#2013266080; === >> > &#2013266080; &#2013266080; &#2013266080;'-----R5------' >> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; 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. > >James
Also 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