# DRAM -> However all I want is the capacitor array, (or does a circuit like this even exist)?

Sorry, this is a very odd question, I've however exhausted my google-fu and I don't even know what question to ask to get the information that I'm looking for. (I'm a programmer so pardon the lack of electronics lingo, as this isn't my specialization).

I'm looking for a component that has the same setup as a dram chip (specifically the capacitor array and if possible the row/column decoder for addressing). I need to store a series of analog low voltage values for a very brief period of time (and signal loss as the capacitor 'bleeds' is acceptable).

Does a circuit like this exist? If so what's it called?

Ps. I'm asking from a programmer perspective, however I need something like this for a project I'm working on. Any help with a starting block would be huge, even a name of a component that has that setup.

• This is an odd question indeed and it is highly likely that the thing you are thinking of will not work. Better describe your intended application and why a digital storage is not good enough for you.. – Eugene Sh. Nov 7 '17 at 17:39
• "very brief" and "low voltage" will mean completely different things to different people. Be more specific and give an idea of how many values you want to store. – Finbarr Nov 7 '17 at 17:43
• It will work and such ICs used to exist, but shopping questions are off-topic. IC questions should be on-topic but they are currently not. – pipe Nov 7 '17 at 17:47
• @pipe A general name would be on topic, I guess. It's like "what is the name of a component which will output logical 1 iff all of it's inputs are 1". – Eugene Sh. Nov 7 '17 at 17:49
• is this what you're after? – Neil_UK Nov 7 '17 at 17:53

I might have read this wrong, however, you are not going to get the functionality you desire in an array. Nobody makes an IC that stores an analog value in an array, if there is anything its custom.

You can use IC's such as the LT1043 that have fast switching capabilities to 'store' voltage values in a capacitor. There are 4 switches per chip. Shown below is an example of how you would wire it to an instrumentation amplifier to provide chopping action to modulate DC for lower noise, but you can wire it to anything you like.

• Bugger, this is close to what I'm looking for but still off. – Metric Nov 7 '17 at 18:08
• Like I said, if your looking for addressing, your not going to find it in an IC, you'll have to 'roll your own'. IC's are produced when there is sufficient commercial demand for such a circuit. – Voltage Spike Nov 7 '17 at 18:11

What you're describing almost sounds like a bucket-brigade device. These devices acted almost like a shift register for analog values, and were sometimes used to implement audio reverb or echo effects. However, they're essentially unavailable today, having been entirely replaced by digital effects.

• Transferring an analog signal from one circuit to another 512 times sounds like it would be massively harder, and introduce massively more noise, than having 512 capacitors along with 512 switches to connect one cap to the output of one voltage follower and 512 to connect the next cap to the input of another voltage follower. Would a 512-sample BBD internally copy each sample through 512 caps, or was that just a behavioral description? – supercat Nov 7 '17 at 19:04
• @supercat Yes -- it's every bit as lossy a process as you might expect. There's a reason nobody makes them anymore. :) – duskwuff -inactive- Nov 7 '17 at 19:15
• Why not use an array of 512 caps, 512 input switches, and 512 output switches, along with a couple voltage followers? I would think that would be cheaper and offer better performance. – supercat Nov 7 '17 at 19:56
• @supercat That would have been a lot harder to fabricate. Keep in mind that these parts were manufactured as early as 1975 -- adding gates to make the array addressable would have forced the manufacturer to reduce the capacity of the array. – duskwuff -inactive- Nov 7 '17 at 20:23
• The bucket brigade idea is still in use on non-cmos based digital cameras. These CCD cameras appear at the high end now. en.wikipedia.org/wiki/Charge-coupled_device – horta Nov 7 '17 at 20:41