T
Terry Given
Guest
What level of GBW production spread should I assume for worst-case
testing? the opamp is a TLV274, GBW 3MHz or so.
Cheers
Terry
testing? the opamp is a TLV274, GBW 3MHz or so.
Cheers
Terry
P
Pooh Bear
Guest
Terry Given wrote:
bifet audio spec op-amps with a typical 4 MHz GBW had dropped to 3MHz or
thereabouts.
Caused the product to fail a specific test. We swapped the part out for
its second source cousin. The affected parts were fine elsewhere.
Graham
I came across an entertaining production problem once where a batch of
bifet audio spec op-amps with a typical 4 MHz GBW had dropped to 3MHz or
thereabouts.
Caused the product to fail a specific test. We swapped the part out for
its second source cousin. The affected parts were fine elsewhere.
Graham
C
Chris Jones
Guest
Terry Given wrote:
capacitors typically have +/- 20% or so tolerance for each type of
component. In practice the variation is likely to be much less unless they
switch to a different fab or shrink the die etc. Whether you would believe
that it is worth planning for a worst case variation in both R and C
simultaneously is up to you.
Chris Jones
I don't know what process that part is on, but on-chip resistors and
capacitors typically have +/- 20% or so tolerance for each type of
component. In practice the variation is likely to be much less unless they
switch to a different fab or shrink the die etc. Whether you would believe
that it is worth planning for a worst case variation in both R and C
simultaneously is up to you.
Chris Jones
J
John Larkin
Guest
On Fri, 27 May 2005 12:47:14 +1200, Terry Given <my_name@ieee.org>
wrote:
I read somewhere recently (LTC appnote on thermocouple acquisition, I
think) that opamp gbw and open-loop gain can have bad tc's, so it's
best to way overkill on gain when precision matters.
John
wrote:
I read somewhere recently (LTC appnote on thermocouple acquisition, I
think) that opamp gbw and open-loop gain can have bad tc's, so it's
best to way overkill on gain when precision matters.
John
T
Terry Given
Guest
John Larkin wrote:
still kind of need a guesstimate for GBW range. 2-6MHz is perhaps enough?
Cheers
Terry
I dont care about Aol, only GBW. Its easy to do the simulations, but I
still kind of need a guesstimate for GBW range. 2-6MHz is perhaps enough?
Cheers
Terry
P
Pooh Bear
Guest
Terry Given wrote:
Nice to have that data though. Just been using an Infineon CoolMOS part and
the data sheet shows both typical Ron and another 'worst case' curve for 98%
of all devices. They don't say how bad the other 2% are though !
Graham
Easily I would say. +/- 1MHz would be my guess.
Nice to have that data though. Just been using an Infineon CoolMOS part and
the data sheet shows both typical Ron and another 'worst case' curve for 98%
of all devices. They don't say how bad the other 2% are though !
Graham
T
Terry Given
Guest
Pooh Bear wrote:
lifetime figure they quoted on the datasheet was 3 sigma *below* the
production mean, which was IIRC twice rated.
Cheers
Terry
FWIW I was once privy to "real" Hitachi electrolytic cap data. The
lifetime figure they quoted on the datasheet was 3 sigma *below* the
production mean, which was IIRC twice rated.
Cheers
Terry
J
Jim Thompson
Guest
On Fri, 27 May 2005 12:47:14 +1200, Terry Given <my_name@ieee.org>
wrote:
that they can be ignored.
Resistors are typically +/- 20%
Capacitors are typically +/- 15%
GBW is proportional to 1/RC
So you're looking at 0.725x < GBW < 1.47x
BUT, The data sheet will usually specify a minimum, so max GBW would
be ~2x the specification minimum.
(TC's ignored, but typically inconsequential.)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice
480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
wrote:
The compensation corner is sufficiently below the transistor effects
that they can be ignored.
Resistors are typically +/- 20%
Capacitors are typically +/- 15%
GBW is proportional to 1/RC
So you're looking at 0.725x < GBW < 1.47x
BUT, The data sheet will usually specify a minimum, so max GBW would
be ~2x the specification minimum.
(TC's ignored, but typically inconsequential.)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice
480)460-2350 | || E-mail Address at Website Fax
480)460-2142 | Brass Rat || http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
T
Terry Given
Guest
Jim Thompson wrote:
thanks for that - exactly what I/m looking for. Archived with thanks
Cheers
Terry
Hi Jim,
thanks for that - exactly what I/m looking for. Archived with thanks
Cheers
Terry
K
Kevin Aylward
Guest
Terry Given wrote:
Av=gm.Xc
where, gm is 40Ic, Xc is the capaciter reactance. Gm is not a resister.
However, this current is ultimately set by a resister, somewhere.
Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
Note that GBW is usually determined by:Jim Thompson wrote:
On Fri, 27 May 2005 12:47:14 +1200, Terry Given <my_name@ieee.org
wrote:
What level of GBW production spread should I assume for worst-case
testing? the opamp is a TLV274, GBW 3MHz or so.
Cheers
Terry
The compensation corner is sufficiently below the transistor effects
that they can be ignored.
Resistors are typically +/- 20%
Capacitors are typically +/- 15%
GBW is proportional to 1/RC
So you're looking at 0.725x < GBW < 1.47x
BUT, The data sheet will usually specify a minimum, so max GBW would
be ~2x the specification minimum.
(TC's ignored, but typically inconsequential.)
...Jim Thompson
Hi Jim,
thanks for that - exactly what I/m looking for. Archived with thanks
Av=gm.Xc
where, gm is 40Ic, Xc is the capaciter reactance. Gm is not a resister.
However, this current is ultimately set by a resister, somewhere.
Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
W
Winfield Hill
Guest
Kevin Aylward wrote...
--
Thanks,
- Win
Jim's simplification, GBW proportional to 1/RC, still holds.
--
Thanks,
- Win
J
Jim Thompson
Guest
On 5 Jun 2005 05:02:52 -0700, Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:
current set by a PTAT, keeping gm relatively flat.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:
"Somewhere" = the bias setup. The better designs have the tail
current set by a PTAT, keeping gm relatively flat.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice
480)460-2350 | || E-mail Address at Website Fax
480)460-2142 | Brass Rat || http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
K
Kevin Aylward
Guest
Winfield Hill wrote:
resister".
Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
Yes, but thats what I meant by "this current is ultimately set by a
resister".
Kevin Aylward
informationEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.