Chip with simple program for Toy

[Paul Keinanen]

On Sat, 21 Jun 2008 15:25:38 -0700 (PDT), bill.sloman@ieee.org wrote:

On Jun 22, 5:52 am, Paul Keinanen <keina...@sci.fi> wrote:

Are you sure that these are ordinary inductors or just a wire through
a ferrite bead?

While the ferrite will increase the inductance, a suitable ferrite
material is also quite lossy at higher frequencies, reducing the risk
for unwanted resonances with the capacitors.

Sadly, you can't rely on this. I've had to put little resistors in
series with ferrite bead to kill a resonance - admittedly at a few
hundred kHz, where the bead doesn't look that lossy.

It would be quite hard to find material that would be lossy at such
low frequencies. For instance materials listed at
http://www.fair-rite.com/newfair/materials.htm start at 1 MHz
(material 31), while the common material 73 have significant losses
only above 10 MHz.

Paul

 

[John Larkin]

On Sat, 21 Jun 2008 15:57:35 GMT, "Talal Itani" <titani@verizon.net>
wrote:

Evil as in Sinner?

Yes.

John

 

[qrk]

On Sat, 21 Jun 2008 16:06:02 GMT, "Talal Itani" <titani@verizon.net>
wrote:

Hello,

I was looking at the schematics for a DSP-based board, running at 100 MHz.
They have a tiny inductor with every bypass cap around the DSP. Do you
think this is necessary? This DSP has analog stuff built-in. If we do not
need analog, can the inductors be eliminated?

Thanks,
T.I.

Seems a bit overkill. If there is a supply running a PLL circuit in
the DSP, you'll need the bead on the PLL supply. Look at the
manufacturer's data sheet. Often, they will recommend bypass capacitor
issues.

---
Mark

 

[Robert Baer]

Talal Itani wrote:

So, there is PCBexpress, and expressPCB. Two different companies?




"Tim Wescott" <tim@seemywebsite.com> wrote in message
newsaydneRCzL9Vv8DVnZ2dnUVZ_uCdnZ2d@web-ster.com...

Talal Itani wrote:

Hello,

I need to have a 4-layer board made, a prototype, 2 boards, nothing
fancy. I did some research in this newsgroup and I narrowed it down to
Sierra Pro Express, ExpressPCB, and AC Advanced Circuits. Do you think I
made the right choice? Do you have any recommendations? I would like to
receive the board 3-5 days.

T.I.

I have only ever used PCB express (NOT express PCB), and they have never
steered me wrong. Nor have they caused problems that I know of for my one
local client that uses them. They're fast, they're accurate, and if your
board comes back with problems it's because you put them there.

I can't speak to any of the others -- they may be even better than PCB
express (although there's not much room for improvement) or they may be
horrid.

http://www.pcbexpress.com/.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html



Absolutely!

 

[Robert Baer]

mpm wrote:

On Jun 21, 10:53�am, Hauke D <hau...@zero-g.net> wrote:

Hi,

I've had good experiences with Advanced Circuits (http://www.
4pcb.com/). Make sure to use their free FDM service (http://www.freedfm.com/), even if you don't end up going with them for
manufacturing.

ExpressPCB is only good for quick-and-dirty stuff. Their advantage is
that they're cheap and their design software is pretty simple to use,
but the big disadvantage is that it locks you in to their software.
Also I've never done 4-layer stuff with them; I believe they're also
kind of limited in that department. They're great for quick-and-dirty
stuff though.

Regards,
-- Hauke D

On Jun 21, 4:19 pm, "Talal Itani" <tit...@verizon.net> wrote:




Hello,

I need to have a 4-layer board made, a prototype, 2 boards, nothing fancy.
I did some research in this newsgroup and I narrowed it down to Sierra Pro
Express, ExpressPCB, and AC Advanced Circuits. �Do you think I made the
right choice? �Do you have any recommendations? �I would like to receive the
board 3-5 days.

T.I.- Hide quoted text -

- Show quoted text -


I've used ExpressPCB for small projects before, but always 2-layer
stuff.
I've never had a problem with them, or their boards.

As for being "locked-in" to their software, for an extra $60 (last
time I checked), they will send you the Gerber files. From there, you
can import to many of the other programs avail.

Also, I recall hearing a while ago that a lot of these PCB prototype
houses are all built at the same place anyway. So, while you might
see 10 different company names (i.e., resellers), the boards
themselves all come from the same place. Sorry, I don't remember the
names of the companies involved, and don't know whether ExpressPCB is
one of them.

-mpm
ExpressPCB stuff comes from Mulino OR and at one time i knew the name

of the "parent" company that will do much "fancier" boards.

 

[Robert Baer]

Talal Itani wrote:

Can ExpressPCB receive files from other PCB software?



I've had good experiences with Advanced Circuits (http://www.
4pcb.com/). Make sure to use their free FDM service
(http://www.freedfm.com/), even if you don't end up going with them for
manufacturing.

ExpressPCB is only good for quick-and-dirty stuff. Their advantage is
that they're cheap and their design software is pretty simple to use,
but the big disadvantage is that it locks you in to their software.
Also I've never done 4-layer stuff with them; I believe they're also
kind of limited in that department. They're great for quick-and-dirty
stuff though.

Regards,
-- Hauke D

On Jun 21, 4:19 pm, "Talal Itani" <tit...@verizon.net> wrote:




Hello,

I need to have a 4-layer board made, a prototype, 2 boards, nothing
fancy.
I did some research in this newsgroup and I narrowed it down to Sierra
Pro
Express, ExpressPCB, and AC Advanced Circuits. ?Do you think I made the
right choice? ?Do you have any recommendations? ?I would like to receive
the
board 3-5 days.

T.I.- Hide quoted text -

- Show quoted text -


I've used ExpressPCB for small projects before, but always 2-layer
stuff.
I've never had a problem with them, or their boards.

As for being "locked-in" to their software, for an extra $60 (last
time I checked), they will send you the Gerber files. From there, you
can import to many of the other programs avail.

Also, I recall hearing a while ago that a lot of these PCB prototype
houses are all built at the same place anyway. So, while you might
see 10 different company names (i.e., resellers), the boards
themselves all come from the same place. Sorry, I don't remember the
names of the companies involved, and don't know whether ExpressPCB is
one of them.

-mpm


They are not set up to do that.

Send a query to their support smail address.

 

[Robert Baer]

Joerg wrote:

Talal Itani wrote:

Can ExpressPCB receive files from other PCB software?


I've had good experiences with Advanced Circuits (http://www.
4pcb.com/). Make sure to use their free FDM service
(http://www.freedfm.com/), even if you don't end up going with them for
manufacturing.

ExpressPCB is only good for quick-and-dirty stuff. Their advantage is
that they're cheap and their design software is pretty simple to use,
but the big disadvantage is that it locks you in to their software.
Also I've never done 4-layer stuff with them; I believe they're also
kind of limited in that department. They're great for quick-and-dirty
stuff though.

Regards,
-- Hauke D

On Jun 21, 4:19 pm, "Talal Itani" <tit...@verizon.net> wrote:



Hello,
I need to have a 4-layer board made, a prototype, 2 boards, nothing
fancy.
I did some research in this newsgroup and I narrowed it down to
Sierra Pro
Express, ExpressPCB, and AC Advanced Circuits. ?Do you think I made the
right choice? ?Do you have any recommendations? ?I would like to
receive the
board 3-5 days.
T.I.- Hide quoted text -

- Show quoted text -


I've used ExpressPCB for small projects before, but always 2-layer
stuff.
I've never had a problem with them, or their boards.

As for being "locked-in" to their software, for an extra $60 (last
time I checked), they will send you the Gerber files. From there, you
can import to many of the other programs avail.


Then if you need to make a little change it'll be another $60?


Also, I recall hearing a while ago that a lot of these PCB prototype
houses are all built at the same place anyway. So, while you might
see 10 different company names (i.e., resellers), the boards
themselves all come from the same place. Sorry, I don't remember the
names of the companies involved, and don't know whether ExpressPCB is
one of them.


I have also used 4PCB, quite happy so far. They only messed up once
(unapproved Gerber edits) but made good on that with an additional fast
run, on the house. The nice thing is that I always have a real contact
person there. She really helped us when they defaulted to this dreaded
RoHS process which we absolutely did not want.

Well, there are Gerber editors...

 

[Robert Baer]

Joerg wrote:

Talal Itani wrote:

Can ExpressPCB receive files from other PCB software?


I've had good experiences with Advanced Circuits (http://www.
4pcb.com/). Make sure to use their free FDM service
(http://www.freedfm.com/), even if you don't end up going with them for
manufacturing.

ExpressPCB is only good for quick-and-dirty stuff. Their advantage is
that they're cheap and their design software is pretty simple to use,
but the big disadvantage is that it locks you in to their software.
Also I've never done 4-layer stuff with them; I believe they're also
kind of limited in that department. They're great for quick-and-dirty
stuff though.

Regards,
-- Hauke D

On Jun 21, 4:19 pm, "Talal Itani" <tit...@verizon.net> wrote:



Hello,
I need to have a 4-layer board made, a prototype, 2 boards, nothing
fancy.
I did some research in this newsgroup and I narrowed it down to
Sierra Pro
Express, ExpressPCB, and AC Advanced Circuits. ?Do you think I made the
right choice? ?Do you have any recommendations? ?I would like to
receive the
board 3-5 days.
T.I.- Hide quoted text -

- Show quoted text -


I've used ExpressPCB for small projects before, but always 2-layer
stuff.
I've never had a problem with them, or their boards.

As for being "locked-in" to their software, for an extra $60 (last
time I checked), they will send you the Gerber files. From there, you
can import to many of the other programs avail.


Then if you need to make a little change it'll be another $60?


Also, I recall hearing a while ago that a lot of these PCB prototype
houses are all built at the same place anyway. So, while you might
see 10 different company names (i.e., resellers), the boards
themselves all come from the same place. Sorry, I don't remember the
names of the companies involved, and don't know whether ExpressPCB is
one of them.


I have also used 4PCB, quite happy so far. They only messed up once
(unapproved Gerber edits) but made good on that with an additional fast
run, on the house. The nice thing is that I always have a real contact
person there. She really helped us when they defaulted to this dreaded
RoHS process which we absolutely did not want.

Not much differnce between tin/lead solder on pads and silver plate

*IF* one is not going above (say) 150C.
Tin/lead solder and tin/silver solders act esentially the same, so
what is the beef?

 

[Robert Baer]

Talal Itani wrote:

Hello,

I was looking at the schematics for a DSP-based board, running at 100 MHz.
They have a tiny inductor with every bypass cap around the DSP. Do you
think this is necessary? This DSP has analog stuff built-in. If we do not
need analog, can the inductors be eliminated?

Thanks,
T.I.


Maybe they are showing parasitic inductance of the leads (part plus cap)?

Look at the accompanying literature.

 

On Jun 22, 5:15 pm, qrk <SpamT...@spam.net> wrote:

On Sat, 21 Jun 2008 16:06:02 GMT, "Talal Itani" <tit...@verizon.net
wrote:

Hello,

I was looking at the schematics for a DSP-based board, running at 100 MHz.
They have a tiny inductor with every bypass cap around the DSP.  Do you
think this is necessary?  This DSP has analog stuff built-in.  If we do not
need analog, can the inductors be eliminated?

Thanks,
T.I.

Seems a bit overkill. If there is a supply running a PLL circuit in
the DSP, you'll need the bead on the PLL supply. Look at the
manufacturer's data sheet. Often, they will recommend bypass capacitor
issues.

The Texas Instruments application note for this part doesn't inspire
confidence. It might be worth looking at what other - more trustworth
- manufacturers recommend for comparable parts. I've had a couple of
bad experiences with Texas Instruments and really don't trust their
customer support, but even the best of companies - Analog Devices come
to mind - aren't infallible.

--
Bill Sloman, Nijmegen

 

[Rich Webb]

On Sun, 22 Jun 2008 11:48:21 GMT, "Talal Itani" <titani@verizon.net>
wrote:

Hello,

At work we have an Intronix Logicport PC based logic analyzer. It is good,
I like using it, but it has very little memory (2048 samples). Can you
recommend something?

Are you using it in transition mode? (Setup | Sample Mode | Compression)

I've been using one of these for years. I do occasionally wish for
deeper storage but I've found that with a little thought I can define
the trigger condition that I need to capture the event of interest.

--
Rich Webb Norfolk, VA

 

[Blarp]

To throw a different tack on the subject: what probes do you use?

When trying to find glitches, faulty wave shapes and such in fast cpu
busses, I find the probes being the bottle neck rather than the scope
BW.

I found myself creating probes based on e.g.
http://www.sigcon.com/Pubs/straight/probes.htm

....allowing me to see things on a lowly 100 MHz scope that would not
be revealed on any high grade scope with (good quality) 1/10 or 1/1
probes.

SW sequence related issues are usually solved by clever (written by SW
engineers, not by me SW routines and debug ports. (never needed a
logic analyser).

If everything is OK, but the system stops for no reason, the scope +
appropriate probe comes out. YMMV - so far I get away with it

 

[John Larkin]

On Sun, 22 Jun 2008 15:36:06 +0200, Blarp <dont@bother.com> wrote:

To throw a different tack on the subject: what probes do you use?

When trying to find glitches, faulty wave shapes and such in fast cpu
busses, I find the probes being the bottle neck rather than the scope
BW.

I found myself creating probes based on e.g.
http://www.sigcon.com/Pubs/straight/probes.htm

...allowing me to see things on a lowly 100 MHz scope that would not
be revealed on any high grade scope with (good quality) 1/10 or 1/1
probes.

For regular digital/embedded stuff, on a 100 MHz scope, any probe will
work. When the fuzzies start to matter, a good fet probe is magical.

The way-out extremes are the Tek SD-14 sampling probe, 3 GHz bandwidth
and something like 0.3 pF at the tip. And the HP 54006A passive probe,
6 GHz bandwidth.

SW sequence related issues are usually solved by clever (written by SW
engineers, not by me SW routines and debug ports. (never needed a
logic analyser).

Me neither. The best logic analyzer is in your head; re-read the
source code.

If everything is OK, but the system stops for no reason, the scope +
appropriate probe comes out. YMMV - so far I get away with it

Last week I had a first-article product where the uP wouldn't run
code. Two hours of frustration condensed into one sentence: one of the
data lines must be pulled down by \RESET to tell it to boot in 8-bit
mode, and the schottky diode that does that had a bad solder joint,
and probing the most handy node, the diode lead, fixed the problem
temporarily, and the diode is *under* the eprom.

John

 

[Joerg]

Robert Baer wrote:

Joerg wrote:

Talal Itani wrote:

Can ExpressPCB receive files from other PCB software?


I've had good experiences with Advanced Circuits (http://www.
4pcb.com/). Make sure to use their free FDM service
(http://www.freedfm.com/), even if you don't end up going with them for
manufacturing.

ExpressPCB is only good for quick-and-dirty stuff. Their advantage is
that they're cheap and their design software is pretty simple to use,
but the big disadvantage is that it locks you in to their software.
Also I've never done 4-layer stuff with them; I believe they're also
kind of limited in that department. They're great for quick-and-dirty
stuff though.

Regards,
-- Hauke D

On Jun 21, 4:19 pm, "Talal Itani" <tit...@verizon.net> wrote:



Hello,
I need to have a 4-layer board made, a prototype, 2 boards, nothing
fancy.
I did some research in this newsgroup and I narrowed it down to
Sierra Pro
Express, ExpressPCB, and AC Advanced Circuits. ?Do you think I made
the
right choice? ?Do you have any recommendations? ?I would like to
receive the
board 3-5 days.
T.I.- Hide quoted text -

- Show quoted text -


I've used ExpressPCB for small projects before, but always 2-layer
stuff.
I've never had a problem with them, or their boards.

As for being "locked-in" to their software, for an extra $60 (last
time I checked), they will send you the Gerber files. From there, you
can import to many of the other programs avail.


Then if you need to make a little change it'll be another $60?


Also, I recall hearing a while ago that a lot of these PCB prototype
houses are all built at the same place anyway. So, while you might
see 10 different company names (i.e., resellers), the boards
themselves all come from the same place. Sorry, I don't remember the
names of the companies involved, and don't know whether ExpressPCB is
one of them.


I have also used 4PCB, quite happy so far. They only messed up once
(unapproved Gerber edits) but made good on that with an additional
fast run, on the house. The nice thing is that I always have a real
contact person there. She really helped us when they defaulted to this
dreaded RoHS process which we absolutely did not want.

Not much differnce between tin/lead solder on pads and silver plate
*IF* one is not going above (say) 150C.
Tin/lead solder and tin/silver solders act esentially the same, so
what is the beef?

Non-RoHS parts on a RoHS PCB usually isn't a good idea.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Joerg]

Robert Baer wrote:

Joerg wrote:

Talal Itani wrote:

Can ExpressPCB receive files from other PCB software?


I've had good experiences with Advanced Circuits (http://www.
4pcb.com/). Make sure to use their free FDM service
(http://www.freedfm.com/), even if you don't end up going with them for
manufacturing.

ExpressPCB is only good for quick-and-dirty stuff. Their advantage is
that they're cheap and their design software is pretty simple to use,
but the big disadvantage is that it locks you in to their software.
Also I've never done 4-layer stuff with them; I believe they're also
kind of limited in that department. They're great for quick-and-dirty
stuff though.

Regards,
-- Hauke D

On Jun 21, 4:19 pm, "Talal Itani" <tit...@verizon.net> wrote:



Hello,
I need to have a 4-layer board made, a prototype, 2 boards, nothing
fancy.
I did some research in this newsgroup and I narrowed it down to
Sierra Pro
Express, ExpressPCB, and AC Advanced Circuits. ?Do you think I made
the
right choice? ?Do you have any recommendations? ?I would like to
receive the
board 3-5 days.
T.I.- Hide quoted text -

- Show quoted text -


I've used ExpressPCB for small projects before, but always 2-layer
stuff.
I've never had a problem with them, or their boards.

As for being "locked-in" to their software, for an extra $60 (last
time I checked), they will send you the Gerber files. From there, you
can import to many of the other programs avail.


Then if you need to make a little change it'll be another $60?


Also, I recall hearing a while ago that a lot of these PCB prototype
houses are all built at the same place anyway. So, while you might
see 10 different company names (i.e., resellers), the boards
themselves all come from the same place. Sorry, I don't remember the
names of the companies involved, and don't know whether ExpressPCB is
one of them.


I have also used 4PCB, quite happy so far. They only messed up once
(unapproved Gerber edits) but made good on that with an additional
fast run, on the house. The nice thing is that I always have a real
contact person there. She really helped us when they defaulted to this
dreaded RoHS process which we absolutely did not want.

Well, there are Gerber editors...

Very frowned upon in industry and (usually) off limits in medical. It's
like printing out a picture, editing it with white-out and scanning it
back in. You typically lose the documentation trail. IOW your original
CAD file no longer matches the product.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Joerg]

BobW wrote:

"Talal Itani" <titani@verizon.net> wrote in message
news:suk7k.3904$JL.2049@trnddc05...
To be honest 50uH and 0.1uF is a recipe for disaster. At the most a
ferrite SMT-bead should be used but usually I don't even do that. A nice
full ground plane and a nice full VCC plane is usually best. Problem with
DSP like this is that you need an additional lower voltage supply so now
you are up to three supply planes, meaning you won't get away with less
than a 6-layer board.

If it's super critical you could have the analog supplies come from a
separate regulator but often converters on a chip with fast digital
processing going on are quite disappointing. A bond wire affords only so
much in RF conductivity.

Hint: Carefully read up on power supply sequencing. Best case wriobng
sequencing leads to a locked up DSP, worst case to a dead DSP.

Oh, and please don't top post.

This DSP has 3.3V and 1.8V supply voltages. Can the same plane have both
voltages?

Talal,

You really need some consulting help if you're asking questions like this.
The edge rates of your signals are likely to be very fast, and this requires
some real know-how when it comes to designing the circuitry, clock
distribution and trace lengths, and the general pcb layout. The previous
comment regarding supply sequencing should be heeded, too.

A short answer for you is this:

If you can arrange it, the controlled-impedance traces should couple to (be
adjacent to) solid (unsplit) GND plane layers. Then, you can split your
supply planes as you need. Otherwise, you have to be very careful in routing
your traces so as to avoid coupling gaps which will result in large
high-inductance coupling loops, or add extra decoupling to couple these
split planes near their splits.

You should seek some professional help for your design and/or take a class
in high-speed signal integrity.

I'd agree. Best to get some help now, not after there are problems with
the design, the boss is becoming impatient and it's almost too late.
Talal, get a consultant that is somewhat local or pay him/her to come to
your work place. Then you can learn the main tricks via a coaching process.

Yes, it'll cost money but it is money well spent.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Joerg]

Tim Wescott wrote:

Joerg wrote:
Talal Itani wrote:
Ok, maybe not tiny. I have never seen this before, so I wonder whey
these inductors are there.


Possibly a very young guy did the design. There are people who take a
sledgehammer to hang a picture. Sometimes the sledgehammer then makes
a hole in the wall ;-)


BTW, 50uH isn't really "tiny".


For RF it's huge. Like a sledgehammer. Sledgehammers can cause a lot
of grief.

WHAT? You mean that semiconductor companies hire kids with no real
experience fresh out of college to be applications engineers?

Now THAT would imply that they look at their applications engineers as a
marketing expense, not a profit center.

Well, suffice it to mention one episode: Just after receiving my degree
I met a guy at an airport. Recognized him right away because we happened
to pick up our degrees around the same time. "Hey, what are you doing
now?" ... "Writing application notes for XYZ Corporation". <gasp>

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Bob Monsen]

"Talal Itani" <titani@verizon.net> wrote in message
news:6zk7k.871$9J.437@trnddc06...

One model that I have used is this one:
http://www.dynoninstruments.com/products_elab080.php
It's a DSO, logic analyzer, and waveform generator all in one.
It's only 80 MS/s but for $500 you can't expect much more. I've actually
found
myself using the digital waveform generators on this thing quite often.

Thanks, this is nice, yet I wished it had a higher sampling rate. Are you
aware of any others?

I have a SDS 200A from softDSP. The windows software is crap. The FFT
feature is basically unusable. The triggering is unreliable. The claim of a
200MHz bandwidth is blather, they do 'statistical sampling', which is
basically adding in some random jitter to the sample clock and correlating
it somehow.

OTOH, the unit is small enough to go with your laptop in the same case, and
is useful therefore as an onsite scope. It can store a fairly large buffer,
and allows the possibility of doing things like line monitoring with a very
slow signal (like 1s per division).

It was also very cheap, less than $1k.

I'm not sure I'd buy it again. It does have an SDK (for $200 extra) that
allows the possibility of doing special kinds of monitoring with a custom
display.

$0.02

Regards,
Bob Monsen

 

[Chris_99]

On Jun 21, 10:19 am, "Talal Itani" <tit...@verizon.net> wrote:

Hello,

I need to have a 4-layer board made, a prototype, 2 boards, nothing fancy..
I did some research in this newsgroup and I narrowed it down to Sierra Pro
Express, ExpressPCB, and AC Advanced Circuits.  Do you think I made the
right choice?  Do you have any recommendations?  I would like to receive the
board 3-5 days.

T.I.

I have had great luck with Eagle + www.fast5protos.com

Chris

 

[JosephKK]

On Sat, 21 Jun 2008 12:13:09 GMT, "Talal Itani" <titani@verizon.net>
wrote:

It is nice if we can do mixed signal, but I am sure we have to pay much
more. We will use this scope in the product development lab, for embedded
work. The signal we are working with is 25MHz digital. Rarely we will look
at a clock of 100 MHz. So, I thought 350 MHz analog is what we should get.
Some Tektronix and LeCroy have a very short buffer. The ones with large
buffer start at $5,000. Is one brand better priced than the others?

Thanks.




My boss asked me to evaluate oscilloscopes and to recommend one. I know
Tektronix and LeCroy. Which is better? Are they any others? Ideally,
we would get a 4-channel scope at 300 MHz, with a 5 million sample record
length. Thanks for your advise.

Agilent is the other "big one". In fact Tektronix and Algilent are the
"big two" brands, Lecroy has always come third.

Lecroy have a bad rep for being hard to drive, the newer ones are better
though.

IMO the Agilent's are the easiest and nicest to drive.

The Agilent DSO6034A suits your requirement:
http://www.home.agilent.com/agilent/product.jspx?nid=-536902766.536905498.00&cc=US&lc=eng
300MHz, 8Mpoint memory, 4 channel
A very very nice scope.

You'll need more specific requirements than that to compare scopes in this
category. Any specific uses in mind? e.g. do you need mixed signal
analysis?, high speed serial protocol analysis?, what sample rate?

Dave.

You could check out Rigol or Insteck. I think that they are the
underlying manufacturers for Agilent and Tektronix.