you use a series input resistor for voltage to current conversion.
I really don't understand all the controversy--there ISN'T ANY FEEDBACK. With a low-Z input the amp is open-loop. The 220k resistor is for d.c. bias only; any affect on gain is acknowledged, but incidental and undesirable. You could replace it with
---R---+---R---- | C | ===
if that makes you feel better, but that's more parts for little gain.
If you want to kill all the gain we just went to great lengths to obtain, sure, you can make a standard inverting amplifier + summing junction amplifier, with gain set by R2/R1.
Again, the purpose was not to present a general-purpose amplifier design (or any particular amplifier application), just explore the bootstrap. It's cute.
ess you use a series input resistor for voltage to current conversion.
se to
Correct. I said early on the real amplifier for the application would most likely just use a dual op amp, with two inverting amplifiers.
The interesting aspects of this circuit--and the reason for posting-- were the bootstrap, the easy ability to greatly increase gain, convert a resistor into an simulated current source, increase output swing, etc. It's cute.
It has nothing to do with gyrators, feedback, etc. Those all totally miss the boat.
less you use a series input resistor for voltage to current conversion.
t
use to
A two-transistor amp has all sorts of compromises, naturally. You can't get max gain if you use feedback resistors to limit the gain and present a defined input impedance.
But, the goal wasn't to design a general-purpose hi-z input, wideband low-distortion amplifier with particular performance. I was just illustrating the bootstrap. That's it. Two-transistors, lots of gain.
The application doesn't matter. I only explained the input impedance being low as an attempt to get Jim to understand that the "feedback" resistor is for bias only, not a.c. feedback.
Sure, but that takes two extra parts. Stripping them out saves two parts, with little loss of gain.
If I gave the impression of missing the "feedback" aspect, the fault is my writing. The feedback path is quite completely obvious, but relatively inconsequential the test frequency.
erstand
are and
I think Fred and Jim are treating this as a circuit application design problem--values and all--as a specific, optimized, general purpose amplifier design exercise. It's not--it's a bootstrap topology showcase.
The bootstrap cap is one way to do that. John's constant-current collector load also bootstraps the collector resistor impedance, a different way of skinning the cat.
As far as the original problem which inspired this--which is entirely irrelevant to the thread, and which was never going to use this ckt anyhow--all I wanted was a spike out when the transducer got pinged.
you use a series input resistor for voltage to current conversion.
Design an amp with infinite input impedance at all frequencies. Post it here.
Unless you happen to design RF, or want the best s/n ratio.
James said so. But the discussion morphed to the general properties and virtues of bootstrapping, which happens in discussion groups. James didn't seem to mind. Some other people did.
Unless the amp is
If the caps are bigger, it makes a cute audio amp with tons of gain from a 3.3 volt supply. Why that fact would invoke hostility, and not admiration, is strange to me.
Zin is around 2K with the values we've been playing with. It could easily be rescaled for more, if that were a concern.
It's a matter of attitude: given a concept, some people will appreciate it and expand on it and play with it, other people will start whining.
It works.
understand
and
My reward is playing with circuits. Theirs is whining about them.
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
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--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
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you use a series input resistor for voltage to current conversion.
to
understand
and
It now occurs to me that my PNP bootstrap is the same as (Tim's?) "shunt current source" and it's a follower, too, for free.
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
use a series input resistor for voltage to current conversion.
Huh? Write the equation.
No it's not, there's a low pass feedback to the base.
Shame upon you.
For C2 being a transducer, it's fine (when "input" is grounded)... as a voltage amplifier it's mis-analyzed... and! I must say, I'm disappointed in you dagmar... James :-(
I guess being a sycophant pays better than being a good engineer? ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
you use a series input resistor for voltage to current conversion.
We live is a sick, sick world. You'll soon be Obama's science advisor :-( ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
you use a series input resistor for voltage to current conversion.
to
I think you missed the boat. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
Might I make a suggestion... write out the equations.
Then apologize for erring, "There's no feedback".
Larkin sucked you in. ...Jim Thompson
-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
formatting link
| 1962 | I love to cook with wine. Sometimes I even put it in the food.
What's wrong with you? James posted a circuit, and I talked about it. You misunderstood it and whined about it; you keep doing both.
How could I have sucked him in?
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
Hey! dagmar... James! What "university" did you get your degree from? I want to send your "not feedback" statement to your professors
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
ess you use a series input resistor for voltage to current conversion.
Obviously--that's the d.c. bias loop. It's unimportant at 40KHz. Ignoring the base impedance, 220k / (1/ 2pi*40KHz*10nF) = 553. That's enough higher than the amplifier's actual voltage gain as to be unimportant. If it mattered, use a higher series resistor or the "T" network below.
You just misunderstood the posting. I'm interested in topologies and techniques (in this case the bootstrap). John understood.
I think you got off on the wrong track when you thought it was some sort of gyrator.
you use a series input resistor for voltage to current conversion.
Just write out the whole loop equation, then tell me what's important and what's not. And tell me what feedback is not feedback.
I'm really disappointed in you :-(
You should be ashamed, kissing Larkin's ass like that.
No loop equation in 24 hours will tell me what kind of a man you aren't. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
you use a series input resistor for voltage to current conversion.
*You* promised a math analysis and didn't deliver.
You also spoke of "20 dB loop gain with the input grounded", which makes no sense at all. Explain that.
He posted a circuit that works, and you can't (under)stand it. Idiot.
(Hey, it's kind of fun to insult someone who can't respond because he pretends to killfile me.)
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
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