I've done a virtual ground using an op amp as a buffer. This is for a single supply audio filter. So happens, I have a spare op amp from quad. chip. Should I make the spare op amp a buffer too and put it in parallel with the other buffer in hopes that the combination will result a 'super' buffer with a 50% reduction in output Z? Or.. are the buffers going to fight each other?
They'll fight, because their offsets will be different. If the Vos is low enough, you can parallel them using ballast resistors, but you'll always be dissipating (delta Vos)**2/(2*Rballast).
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
1st OpAmp: + terminal is input, - terminal to load, R from OpAmp output to load.
2nd (and subsequent) OpAmps: + terminal to output terminal of 1st OpAmp, - terminal to _this_ OpAmp output, R from _this_ OpAmp output to load. ...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 |
"The source of well-being in this country is employment."
- Steve Wynn, on Fox News Sunday, 11 October 2009
Why not wire the second circuit (including resistor) in parallel with the first (including resistor)? Basically, paralleled voltage followers with current sharing resistors. With your circuit I'd expect some load sharing issues on input transients.
--
| 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 |
If I\'m talking, you should be taking notes.
-- | 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
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| 1962 |
1) You cannot legislate the poor into prosperity by legislating the wealthy out of prosperity.
2) What one person receives without working for, another person must work for, without receiving.
3) The government cannot give to anybody anything that the govern- ment does not first take from somebody else.
4) When half of the people get the idea that they do not have to work because the other half is going to take care of them, and when the other half gets the idea that it does no good to work because somebody else is going to get what they work for, that my dear friend, is the beginning of the end of any nation.
Do you need the reduced Z? I'd just leave it connected as a buffer with grounded input and perhaps use it in the future. I hate quad opamps BTW. Things always seem to get to crowded.
Quad op-amps (and comparators) are the most retarded pinout ever. I will never use an LM339 again...
If it means you'll end up with a pair of e.g. LM358 instead, and one ends up extra, who cares... or you can just do the same thing, and have the pins where you need them this time.
The 339's pinout is great for doing window comparators and other wire-OR type things. Anyway, it takes a microsecond to do anything, and it takes real talent to have pickup or oscillation issues with that sort of speed.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
A 339 pinout is quite good from a noise point of view, since all the outputs are at one end. The usual quad op amp is different, in that each op amps pin's are grouped together. For layout purposes, it doesn't seem to make much odds, but the the 339 can make it easier to fit feedback parts round the device.
Neat. The verbal description was hard work, but a glance at the schematic makes it clear. Higher drive capability and current sharing through the 100r resistors...
Does anyone care. The LM324 and LM339 are probably the _most_used_ jelly bean parts, EVER!
[snip] ...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
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| 1962 |
"I have a dream that [we] will one day live in a nation where [Obama] will not be judged by the color of [his] skin but by the content of [his] character."
Obama will then be impeached.
"Free at last! free at last! Thank God Almighty, we [will be] free at last!"
I actually came up with that before I had access to a simulator. I was driving telephone "muff cup" couplers for 300 Baud modems (~1980 ;-) ...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.
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