DDS based function generators

[MeggerMan]

Hi Earl,
The scope is a Konus Opal #5418 with 2X objective and 10x eyepiece.

I used a Nikon Coolpix 775 (2 megapixels) held at just the right point above one of the eyepieces.
You have to get the angle just right, the height and the position must be in the eyepiece focus centre to get a good circular photo with the cropped edges.

The lighting is provided by a 12W (12V 1 A)halogen lamp built into the scope.

Quite easy to do, no need to pay for an expensive adapter ring.
Although if I did a lot of photos like this, I may actually make up a sort of adapter to fit the camera.
The magnification is only 20x so this could be why the photos are so clear.

Regards
Rob

[MeggerMan]

Hi Jason,

Thanks for the tips. About the RF transformer, I'm intentionally not using that because it's output only works above 200 kHz, which would cut out most of the usable range for Bob's TPU. In my case, I'm simply replacing the transformer wit ha comparator to convert the sine wave into a CMOS computable square wave that I can use the clock the programmable pulse width chips (see attached circuit diagram).

As for the power supply. I like the idea of using the switching supply for greater efficiency, though I'm going to avoid the QFN packages like the plague  . Have you seen any switching converters that have all of the support components contained in one package?

Not sure about the RF transformer now, I misread the spec thinking it could go down to 0.3 Hz, when it really says 0.3MHz or 300KHz, it will probably be fine all the way down to 10Hz or lower, just need to get Mark to test it on his eval board.
The resistors in the diagram, don't they need to be grounded to AGND rather than set to AVDD?
The comparator does look like a preferable method of output - at least the parts are easy to get - although they can be expensive for high speed op-amps like the AD811.

From the AD9959 FAQ I read that the current needs to flow to ground.
With regards to the oscillator, I think I will go with a 125MHz 3.3V low jitter SAW device and use resistors to limit the HI/LO voltage.
I will email the Analog Devices tech support to see what they think.

Regards
Rob

[MeggerMan]

New PCB layout v1.1, not sure if the screw will foul L2 though.

[MarkSnoswell]

I am the proud owner of a brand new AD9959 evaluation board
I'll post pics tonight.

[Jdo300]

OOoooooh I wanna see I wanna see