Cirrus Logic amplifiers

John Popelish · May 9, 2005

I am trying to get a few CS3001 op amps that have almost unbelievable
low frequency noise voltage. But none of the normal distributors I
deal with carry Cirrus Logic. Can anybody tell me where I can get my
hands on a few of these?

Spehro Pefhany · May 9, 2005

On Mon, 09 May 2005 01:09:45 -0400, the renowned John Popelish
<jpopelish@rica.net> wrote:

I am trying to get a few CS3001 op amps that have almost unbelievable
low frequency noise voltage. But none of the normal distributors I
deal with carry Cirrus Logic. Can anybody tell me where I can get my
hands on a few of these?

Newark have them in stock.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

John Popelish · May 9, 2005

Spehro Pefhany wrote:

On Mon, 09 May 2005 01:09:45 -0400, the renowned John Popelish
jpopelish@rica.net> wrote:

I am trying to get a few CS3001 op amps that have almost unbelievable
low frequency noise voltage. But none of the normal distributors I
deal with carry Cirrus Logic. Can anybody tell me where I can get my
hands on a few of these?

Newark have them in stock.

Hot damn! Thanks.

John Larkin · May 9, 2005

On Mon, 09 May 2005 01:36:11 -0400, John Popelish <jpopelish@rica.net>
wrote:

Spehro Pefhany wrote:
On Mon, 09 May 2005 01:09:45 -0400, the renowned John Popelish
jpopelish@rica.net> wrote:

I am trying to get a few CS3001 op amps that have almost unbelievable
low frequency noise voltage. But none of the normal distributors I
deal with carry Cirrus Logic. Can anybody tell me where I can get my
hands on a few of these?

Newark have them in stock.

Hot damn! Thanks.

Must be a chopper. 50 pF Cin!

John

Spehro Pefhany · May 9, 2005

On Mon, 09 May 2005 17:43:02 -0400, the renowned John Popelish
<jpopelish@rica.net> wrote:

John Larkin wrote:
On Mon, 09 May 2005 01:36:11 -0400, John Popelish <jpopelish@rica.net
wrote:

Spehro Pefhany wrote:

On Mon, 09 May 2005 01:09:45 -0400, the renowned John Popelish
jpopelish@rica.net> wrote:

I am trying to get a few CS3001 op amps that have almost unbelievable
low frequency noise voltage. But none of the normal distributors I
deal with carry Cirrus Logic. Can anybody tell me where I can get my
hands on a few of these?

Newark have them in stock.

Hot damn! Thanks.

Must be a chopper. 50 pF Cin!

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

John Popelish · May 9, 2005

John Larkin wrote:

On Mon, 09 May 2005 01:36:11 -0400, John Popelish <jpopelish@rica.net
wrote:

Spehro Pefhany wrote:

On Mon, 09 May 2005 01:09:45 -0400, the renowned John Popelish
jpopelish@rica.net> wrote:

I am trying to get a few CS3001 op amps that have almost unbelievable
low frequency noise voltage. But none of the normal distributors I
deal with carry Cirrus Logic. Can anybody tell me where I can get my
hands on a few of these?

Newark have them in stock.

Hot damn! Thanks.

Must be a chopper. 50 pF Cin!

The jaw dropper for me was the up to 1000 trillion open loop gain.

Winfield Hill · May 9, 2005

Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

--
Thanks,
- Win

Rich Grise · May 9, 2005

On Mon, 09 May 2005 15:10:51 -0700, Winfield Hill wrote:

Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

LOL!

Thanks! :-D
Rich

John Popelish · May 10, 2005

Winfield Hill wrote:

Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

Weirdly, they are stable at a closed loop gain of 10, but not at a
closed loop gain of 10,000.

John Larkin · May 10, 2005

On Mon, 09 May 2005 22:25:28 -0400, John Popelish <jpopelish@rica.net>
wrote:

Winfield Hill wrote:
Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

Weirdly, they are stable at a closed loop gain of 10, but not at a
closed loop gain of 10,000.

There are a number of weird things about this chip. There are lots of
chopper amps around that have less personality.

John

Robert · May 12, 2005

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:hep1815r4tv8gng7ffg9vc1p6708shfspc@4ax.com...

On Mon, 09 May 2005 22:25:28 -0400, John Popelish <jpopelish@rica.net
wrote:

Winfield Hill wrote:
Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

Weirdly, they are stable at a closed loop gain of 10, but not at a
closed loop gain of 10,000.

There are a number of weird things about this chip. There are lots of
chopper amps around that have less personality.

John

Looked at their web site a bit but couldn't find anything on the "Multipath"
they talk about as a big part of several of their chips including the Amps.
I have a vague recollection from quite a while back (Electronic Design?) of
a "multipath" approach where they split the input frequency range at the
input, each band gets it's own gain path, and then they combine them at the
output. All on chip.

Anybody seen a reference like this?

Robert

Jim Thompson · May 12, 2005

On Thu, 12 May 2005 23:29:01 GMT, "Robert" <Robert@yahoo.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:hep1815r4tv8gng7ffg9vc1p6708shfspc@4ax.com...
On Mon, 09 May 2005 22:25:28 -0400, John Popelish <jpopelish@rica.net
wrote:

Winfield Hill wrote:
Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

Weirdly, they are stable at a closed loop gain of 10, but not at a
closed loop gain of 10,000.

There are a number of weird things about this chip. There are lots of
chopper amps around that have less personality.

John

Looked at their web site a bit but couldn't find anything on the "Multipath"
they talk about as a big part of several of their chips including the Amps.
I have a vague recollection from quite a while back (Electronic Design?) of
a "multipath" approach where they split the input frequency range at the
input, each band gets it's own gain path, and then they combine them at the
output. All on chip.

Anybody seen a reference like this?

Robert

Are you perhaps thinking of "feed-forward"? Higher frequencies are
fed around the DC-accuracy (limited bandwidth sections), resulting in
a substantial improvement in usable gain-bandwidth product.

...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

Robert · May 13, 2005

"Jim Thompson" <thegreatone@example.com> wrote in message
news:jdq781lrv44btd7cgp6t3ho11bjc13jtb3@4ax.com...

On Thu, 12 May 2005 23:29:01 GMT, "Robert" <Robert@yahoo.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
news:hep1815r4tv8gng7ffg9vc1p6708shfspc@4ax.com...
On Mon, 09 May 2005 22:25:28 -0400, John Popelish <jpopelish@rica.net
wrote:

Winfield Hill wrote:
Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

Weirdly, they are stable at a closed loop gain of 10, but not at a
closed loop gain of 10,000.

There are a number of weird things about this chip. There are lots of
chopper amps around that have less personality.

John

Looked at their web site a bit but couldn't find anything on the
"Multipath"
they talk about as a big part of several of their chips including the
Amps.
I have a vague recollection from quite a while back (Electronic Design?)
of
a "multipath" approach where they split the input frequency range at the
input, each band gets it's own gain path, and then they combine them at
the
output. All on chip.

Anybody seen a reference like this?

Robert

Are you perhaps thinking of "feed-forward"? Higher frequencies are
fed around the DC-accuracy (limited bandwidth sections), resulting in
a substantial improvement in usable gain-bandwidth product.

...Jim Thompson

Doesn't sound like what I vaguely remember but I definitely could be
mistaken.

Robert

Winfield Hill · May 13, 2005

Robert wrote...

Are you perhaps thinking of "feed-forward"? Higher frequencies are
fed around the DC-accuracy (limited bandwidth sections), resulting
in a substantial improvement in usable gain-bandwidth product.

...Jim Thompson

Doesn't sound like what I vaguely remember but I definitely could
be mistaken.

Establishing a feed-forward path is an extremely useful scheme
in opamp circuits, which I first learned from Robert Widlar in
the 60s. He elaborated in app notes for NSC's LM301A opamp,
which he designed. Robert at Yahoo, I can recommend it to you.

--
Thanks,
- Win

Spehro Pefhany · May 13, 2005

On Fri, 13 May 2005 06:15:59 GMT, the renowned "Robert"
<Robert@yahoo.com> wrote:

"Jim Thompson" <thegreatone@example.com> wrote in message
news:jdq781lrv44btd7cgp6t3ho11bjc13jtb3@4ax.com...
On Thu, 12 May 2005 23:29:01 GMT, "Robert" <Robert@yahoo.com> wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
message
news:hep1815r4tv8gng7ffg9vc1p6708shfspc@4ax.com...
On Mon, 09 May 2005 22:25:28 -0400, John Popelish <jpopelish@rica.net
wrote:

Winfield Hill wrote:
Spehro Pefhany wrote...

The jaw dropper for me was the up to 1000 trillion open loop gain.

Yes, that should pretty much eliminate it from the error budget.

Right, at 0.0000001 Hz, etc.

Weirdly, they are stable at a closed loop gain of 10, but not at a
closed loop gain of 10,000.

There are a number of weird things about this chip. There are lots of
chopper amps around that have less personality.

John

Looked at their web site a bit but couldn't find anything on the
"Multipath"
they talk about as a big part of several of their chips including the
Amps.
I have a vague recollection from quite a while back (Electronic Design?)
of
a "multipath" approach where they split the input frequency range at the
input, each band gets it's own gain path, and then they combine them at
the
output. All on chip.

Anybody seen a reference like this?

Robert

Are you perhaps thinking of "feed-forward"? Higher frequencies are
fed around the DC-accuracy (limited bandwidth sections), resulting in
a substantial improvement in usable gain-bandwidth product.

...Jim Thompson

Doesn't sound like what I vaguely remember but I definitely could be
mistaken.

Robert

Here's a press release on another similar (earlier) Cirrus product:

http://www.cirrus.com/en/press/releases/P26.html

and the current one:
http://www.cirrus.com/en/press/releases/P311.html

getting more technical:
http://www.imec.be/esscirc/ESSCIRC2002/PDFs/C08.04.pdf
"It is targeted towards the applications where the
input signal is low frequency < 1kHz and the signal level
is in mV range and a high THD is required."

There seems to be an IEEE paper here but I don't have a subscription:
"A Five Stage Chopper Stabilized Instrumentation Amplifier..."
http://www.google.com/url?sa=U&start=1&q=http://ieeexplore.ieee.org/iel4/5639/15113/00688092.pdf%3Farnumber%3D688092&e=747

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Winfield Hill · May 13, 2005

Spehro Pefhany wrote...

There seems to be an IEEE paper here but I don't have a subscription:
"A Five Stage Chopper Stabilized Instrumentation Amplifier..."

Axel Thomsen, June 1998. "A Five-Stage Chopper-Stabilized Instrumentation
Amplifier Using Feedforward Compensation," Proc, Symposium on VLSI Circuits.

--
Thanks,
- Win

John Popelish · May 13, 2005

Spehro Pefhany wrote:

Here's a press release on another similar (earlier) Cirrus product:

http://www.cirrus.com/en/press/releases/P26.html

and the current one:
http://www.cirrus.com/en/press/releases/P311.html

getting more technical:
http://www.imec.be/esscirc/ESSCIRC2002/PDFs/C08.04.pdf
"It is targeted towards the applications where the
input signal is low frequency < 1kHz and the signal level
is in mV range and a high THD is required."

The gain and phase curves in this one look very similar to those of
the CS3001.

Spehro Pefhany · May 13, 2005

On Fri, 13 May 2005 10:04:14 -0400, the renowned John Popelish
<jpopelish@rica.net> wrote:

Spehro Pefhany wrote:

Here's a press release on another similar (earlier) Cirrus product:

http://www.cirrus.com/en/press/releases/P26.html

and the current one:
http://www.cirrus.com/en/press/releases/P311.html

getting more technical:
http://www.imec.be/esscirc/ESSCIRC2002/PDFs/C08.04.pdf
"It is targeted towards the applications where the
input signal is low frequency < 1kHz and the signal level
is in mV range and a high THD is required."

The gain and phase curves in this one look very similar to those of
the CS3001.

One interesting thing to me in the above paper is the icky "small
oscillation" that occurs when the output approaches the supply rails
from either direction. If you were expecting it to saturate
gracefully, this could be a nasty, nasty gotcha (assuming the CS3001
does the same thing, which it may not).

Of course, they don't mention it in the CS3001 datasheet, so surely it
must be okay, right? ;-)

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Robert · May 15, 2005

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:gp7981hbmgflr42o9tqmh8a366eoaml1uf@4ax.com...
[snip]

Looked at their web site a bit but couldn't find anything on the
"Multipath"
they talk about as a big part of several of their chips including the
Amps.
I have a vague recollection from quite a while back (Electronic Design?)
of
a "multipath" approach where they split the input frequency range at the
input, each band gets it's own gain path, and then they combine them at
the
output. All on chip.

Anybody seen a reference like this?

Robert

Are you perhaps thinking of "feed-forward"? Higher frequencies are
fed around the DC-accuracy (limited bandwidth sections), resulting in
a substantial improvement in usable gain-bandwidth product.

...Jim Thompson

Doesn't sound like what I vaguely remember but I definitely could be
mistaken.

Robert

Here's a press release on another similar (earlier) Cirrus product:

http://www.cirrus.com/en/press/releases/P26.html

and the current one:
http://www.cirrus.com/en/press/releases/P311.html

getting more technical:
http://www.imec.be/esscirc/ESSCIRC2002/PDFs/C08.04.pdf
"It is targeted towards the applications where the
input signal is low frequency < 1kHz and the signal level
is in mV range and a high THD is required."

There seems to be an IEEE paper here but I don't have a subscription:
"A Five Stage Chopper Stabilized Instrumentation Amplifier..."
http://www.google.com/url?sa=U&start=1&q=http://ieeexplore.ieee.org/iel4/5639/15113/00688092.pdf%3Farnumber%3D688092&e=747

Best regards,
Spehro Pefhany

Thanks. Will try to find a copy.

Robert

John Larkin · May 15, 2005

On 13 May 2005 04:40:02 -0700, Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Robert wrote...

Are you perhaps thinking of "feed-forward"? Higher frequencies are
fed around the DC-accuracy (limited bandwidth sections), resulting
in a substantial improvement in usable gain-bandwidth product.

...Jim Thompson

Doesn't sound like what I vaguely remember but I definitely could
be mistaken.

Establishing a feed-forward path is an extremely useful scheme
in opamp circuits, which I first learned from Robert Widlar in
the 60s. He elaborated in app notes for NSC's LM301A opamp,
which he designed. Robert at Yahoo, I can recommend it to you.

It was done in the tube days, using a mechanical chopper stage to add
lf gain and dc stability to a tube opamp.

John

Cirrus Logic amplifiers

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