High speed analog memory

[pisoiu]

analog memory

Hi,
Anyone knows who manufacture high speed analog memories, used as an alternative to ADC in high speed DSO? Thanks,

/pisoiu

 

[xvibe]

5gsps high speed adc

I didn't know that type of memorie exits!
Could you tell me how they work, how are they made, etc...

 

[pisoiu]

spie-atwd.pdf

It seem they exist, and are sometimes called switched capacitor arrays. Works quite similar with FIFO digital memories, but with analog signals. They are an alternative for high speed sampling systems such as dso (fluke has a 2,5gsps portable dso based on this principle). But I have the impression that this memories are integrated in custom ICs. For example, TDS2014 Tektronix DSO (4ch x 1Gsps) have 2 chips inside in analog part made by National, and they are custom chips. Not a piece of informations on the net about them.

/pisoiu

Edited: These chips are also called ATWD (Advanced Transient Waveform Digitiser).

 

[Basil]

fast analog memory

CCD arrays are no fast

 

[flatulent]

EGG Reticon once made these and may still make them. The problem with these is that the analog voltage is stored as a charge. If you circulate the output to the input and cycle the charges through, the signal gets degraded on each pass through the system. If you read the signal in fast and then clock it out slowly, there is still a degrading caused by the charges at each stage draining off as it sits there.

 

[pisoiu]

EGG Reticon once made these and may still make them. The problem with these is that the analog voltage is stored as a charge. If you circulate the output to the input and cycle the charges through, the signal gets degraded on each pass through the system. If you read the signal in fast and then clock it out slowly, there is still a degrading caused by the charges at each stage draining off as it sits there.

Thanks. The problem is obvious due to losses in capacitive elements. It seems that Tektronix use this method in some of their DSO, and I think this is the origin of their problem with noisy traces with no signal at input. But this method have some advantages. It costs much less for high speed acquisition than the equivalent flash ADC sollution, consumes less power, and I've read some technical papers about experimental chips with performances around 5Gsps for transient recording. When sampling at Gsps range, not only conversion is a problem, but storing of samples is also. ATWD solve this problem as well.

/pisoiu

 

[batdin]

All I know is that there existed fast CCDs more than 10 years ago that were subject of embargo due to their use in real-time radar processors.Nowadays however this function is implemented digitally.

 

[tryagain]

ISS compony
such iss61c256
Bitscope also use it

 

[pisoiu]

ISS compony
such iss61c256
Bitscope also use it

?!?!?! perhaps you are talking about ISSI 61C256, which is pure sram. Read my first post carefully, I was talking about ANALOG memory.

/pisoiu

 

[ME]

But I have the impression that this memories are integrated in custom ICs. For example, TDS2014 Tektronix DSO (4ch x 1Gsps) have 2 chips inside in analog part made by National, and they are custom chips. Not a piece of informations on the net about them.

I don't think Tektronix uses this technology.
Try to read this Tektronix White Paper:
DSP in High Performance Oscilloscopes
www.tek.com/Measurement/App_Notes/55_17589/eng/55W_17589_0.pdf
The paper discusses the technology used inside Tektronix new DSOs.

 

[cherrytart]

The ccd's used in cameras are mostly analog memory devices, you might Google 'high speed ccd limitations" to see what the limitation on the technology are.

The limitations are far higher than I thought, B&W ccds good for 100,000,000 fps.

 

[alphi]

what's analog memory,
How to compare digital memory?

 

[pisoiu]

The ccd's used in cameras are mostly analog memory devices, you might Google 'high speed ccd limitations" to see what the limitation on the technology are.

The limitations are far higher than I thought, B&W ccds good for 100,000,000 fps.

Actually, you can take 5Gsps real using this technology. Alphi, here is your answer **broken link removed**

/pisoiu

 

[electronrancher]

are you looking for sample-and-hold? these are made by many companies such as maxim for use in high speed storage/sampling systems search maxim for sample-and-hold.

 

[pisoiu]

are you looking for sample-and-hold? these are made by many companies such as maxim for use in high speed storage/sampling systems search maxim for sample-and-hold.

Read the article posted by me in the link above. It is sample and hold, but there are many sample and holds, few thousands (depending on how many samples do you want to keep) on the same chip. Furthermore, a delayed clock control line and a low speed adc are placed also on the same chip.

/pisoiu