"Analog" RAM and D-FilpFlop?

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davyzhu

Joined: 23 May 2004
Posts: 521
Helped: 3
Location: oriental

21 Nov 2005 9:33 "Analog" RAM and D-FilpFlop?

Hi all,

We know that digital circuit use RAM and D-FF to store digital signal values. Is there any "Analog" RAM and D-FF which can store analog signal values?

I am curious to know if not, how to store analog signal values in analog way?

Any suggestions will be appreciated!
Best regards,
Davy

echo47

Joined: 07 Apr 2002
Posts: 4206
Helped: 566

21 Nov 2005 9:47 "Analog" RAM and D-FilpFlop?

You can store a current in an inductor (magnetic field), or a voltage in a capacitor (electric field). A charge-coupled device (CCD) stores an array of analog voltages in an array of capacitors. DRAM and some ROMs use capacitors too, and some of them recognize mutiple voltage levels as distinct bits. A magnetic tape recorder ... well, you get the idea!

neoaspilet11

Joined: 29 Sep 2005
Posts: 276
Helped: 21
Location: Cebu, Philippines

21 Nov 2005 9:59 "Analog" RAM and D-FilpFlop?

Hello Davyzhu,
Nice question. I think there is no device that can store an analog signal in analog way. Because when we try to store an analog value say for example voltage, we are trying to store the charges that are impressed on that voltage. There is no other way to do that except using capacitors. There is no pefect capacitor! charges have always have a way to leak making it impossible to contain them.

jonw0224

Joined: 22 Nov 2004
Posts: 199
Helped: 28
Location: USA

21 Nov 2005 18:58 "Analog" RAM and D-FilpFlop?

Keep in mind that in many applications a capacitor is used to store an analog voltage for short periods of time (ex. peak detector, track and hold for ADC, etc).

It may be possible to build a circuit to hold an analog voltage for a while using a capacitor, but you would have many problems b/c you would have charge and discharge cycles on the capacitor and every error on a charge/discharge cycle would be cummulative and eventually, the capacitor would be discharged or charged to the supply voltage.

If a device exists, it would be interesting indeed.

tkbits

Joined: 04 Dec 2004
Posts: 235
Helped: 36

21 Nov 2005 23:08 Re: "Analog" RAM and D-FilpFlop?

Search for "charge coupled devices" or CCDs.

EDIT: I missed seeing this mentioned in echo47's post. He also mentioned magnetic tape storage, as in audio and video tapes.

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sabari

Joined: 02 Oct 2004
Posts: 66
Helped: 1

22 Nov 2005 8:29 "Analog" RAM and D-FilpFlop?

I think there is no device that can store an analog signal in analog way.

Sceadwian

Joined: 25 Sep 2005
Posts: 175
Helped: 13

22 Nov 2005 22:26 "Analog" RAM and D-FilpFlop?

There is no problem storing an analog signal in an analog format, all the above methods work just fine. They also decay over time. Modern ADC and DAC methods are so advanced though that it makes no difference. Using enough bits can in some cases give you more discrete levels than some older analog formats, and they do not decay over time.