40Mhz square wave on Rigol DS1052E, Agilent MSOX3024A, Tek 7104

[KTP]

Since the Tektronix 7104 1 Ghz boat anchor is working again, I thought it might be fun to see what a 40Mhz square wave looks like on my three scopes (a Rigol modded 100mhz DS1052E, a Agilent 200mhz MSOX3024, and the Tektronix 1Ghz mainframe using a 7A29 amplifier and 7B10 timebase).

The signal source is a Epson SG531PH 40.000Mhz clock oscillator module pulled off some random old circuit board.  I soldered it on a little copper board with a 1 inch cable to a bnc connector so it could plug directly into the scope bnc.  There is a 0.1uF cap between power and ground on the little board.

Anyway, the Rigol seems to hold up decently well.  The Agilent looks a little closer to the Tek, especially in the 2nd pic with "fuzz mode" activated.  The Tek I guess is showing us the true waveform filtered through 25 years of aging capacitors, but the period looks like 24ns instead of the correct 25ns.  I guess maybe this could be because it is around 10 years past cal date heh heh.  Note I used 50 ohm input on the Agilent and Tek (it only has 50 ohm inputs) but the Rigol is forced to use 1Meg inputs.  There was some loading of the oscillator and reduced amplitude due to the 50ohm impedance.

Anyway, here are the pictures (the Tek screen protector plastic has some scratches which glare the waveform in the camera, but it is pretty sharp in real life):

[IanB]

What does the Rigol trace look like if you instead use the x10 probe directly on the signal source close to the chip output? (Using the short ground spring if possible rather than the clip lead.)

[KTP]

What does the Rigol trace look like if you instead use the x10 probe directly on the signal source close to the chip output? (Using the short ground spring if possible rather than the clip lead.)

Using one of the Rigol 1x/10x probes set to 10x and using a ground spring from my Agilent probe accessories kit, I got the following waveform:

[KTP]

I added a high quality 10uF ceramic cap on the oscillator board across Vcc and
Ground in addition to the 0.1uF cap that was already there.  This made a small but noticeable improvement in the top of the waveform.  In the picture I have saved the reference waveform in orange with the old board (no 10uF cap) and have the new waveform in yellow displayed on top of it.  Starting to look like a pretty decent 40mhz square wave 

[KTP]

Slightly different now, but I have run the waveform output from the Agilent MSOX3024A into a deadbug NC7NZ34 tinylogic buffer chip.  I paralleled all the buffers such that I can drive 4V into 50 ohms.  The MSOX3024A waveform generator has a rise time of around 16ns, but with this tinylogic buffer, I am getting rise times of about 800ps (as seen on the Tektronix 1Ghz scope...the Agilent scope bandwidth won't let me see that fast).  A very easy, neat edge sharpener...for like $0.20.

In this pic the Tek 7104 is 1V per division, 500ps per division and the Agilent MSOX3024A is 1V per division 5ns per division.  The pulse is the same into both, 20ns 4V fed from Agilent waveform gen through the tinylogic buffer.

[Rosendorfer]

Using one of the Rigol 1x/10x probes set to 10x and using a ground spring from my Agilent probe accessories kit, I got the following waveform:

Hi

Nice example that DS1052E is much much better than the oryginall delivered probes, so  Specaly after hackig it for 100MHz the oryginal probes should be just forgoten and newer used for anything that needs 10x probes.
Thing that maybe is worth to mention for haked rigol owners, now you have 100MHz scope so you need  proper probes. 
And well that 40MHz sqare.... realy looks supisingly  well , probably thanks to direckt connection.

Regards
Rosendorfer

[Mechatrommer]

Thing that maybe is worth to mention for haked rigol owners, now you have 100MHz scope so you need  proper probes. 

this is not specific to rigol. according to Jim Williams, its generally apply to any kind of scope... "the best probe is no probe"

[muvideo]

KTP nice sharp and clean edge that tinylogic ic, I read it's datasheet some time ago but
didnt find the risetime, seem a very good candidate for fast pulse management.
How did you couple the IC output to 7A29 input?

Fabio.

[KTP]

KTP nice sharp and clean edge that tinylogic ic, I read it's datasheet some time ago but
didnt find the risetime, seem a very good candidate for fast pulse management.
How did you couple the IC output to 7A29 input?

Fabio.

I didn't try really hard.  I just mounted the IC deadbug on a .5 inch square copper board with a few flat traces cut out with a razer blade.  The output from all three buffers just feed directly into about 1 inch of coax then a BNC that plugs directly into the scope.  I did put a .1uf and two 10uf ceramic caps across power, ground right next to the tinylogic power pin.

I just got some samples of the Analog ADCMP580 CML comparitor.  It can only swing 400mV into 50ohm, but has about 50ps rise time.  I may try to deadbug it this weekend, but it will be very hard.  Because I only have a 1Ghz scope to test, I won't really know much of how it works.  I like the tinylogic because you can get almost 5V into 50ohms (the tinylogic can drive 32mA per output, so 90mA into 50ohms).

[muvideo]

I just got some samples of the Analog ADCMP580 CML comparitor.  It can only swing 400mV into 50ohm, but has about 50ps rise time.  I may try to deadbug it this weekend, but it will be very hard.  Because I only have a 1Ghz scope to test, I won't really know much of how it works.

Time to get a 7S11

  I like the tinylogic because you can get almost 5V into 50ohms (the tinylogic can drive 32mA per output, so 90mA into 50ohms).

Infact that is why I like it, simple to setup and good voltage range, less than 1nS is more than enough for my "needs".
But I still have to find the 7A29-7B15 for my scope.

Fabio.

[KTP]

I have an extra 7a29 you could have but they are not super small so it would cost more to ship than it is worth.

[muvideo]

I have an extra 7a29 you could have but they are not super small so it would cost more to ship than it is worth.

Ok let's talk about it, I will send a pm.
Fabio.

[KTP]

Just a little bit more on the pulse.

I have set up the Rigol modded DS1052E with a BNC T connector and have used a 50ohm BNC termination right at the input external to the scope.  The Rigol is set to x1 input (1Meg).  The pulse is 20ns, with estimated 700ps to 750ps rise time, approx 4V.  The first pic is the Rigol terminated with this setup...not bad!  The rise time is calculated to be around 2.2nS which at .35/risetime would mean about 150mhz bandwidth.  The second pic is with the normal setup, feeding the pulse directly into the channel 1 BNC with only the scopes internal 1Meg termination.  The pulse looks much worse, and a rise time  measurement is not even really possible.  The third picture is of the setup, showing the tinylogic pulse board and the T type BNC connector.