[sdiy] Analog Computational Unit

[James Patchell]

Yes, those are fun analog computational blocks.  I have used them for 
computing ARCTAN and Square Root Sum of Squares.  However, there is one 
caveat .... the input voltages can only be positive (because they are log 
circuits).  It is possible to get around these limitation.  Also, bandwidth 
is a function of signal level.  At the lower input voltages (lower input 
current really), the bandwidth is significantly lower.  These are just 
things you need to be aware of.  It might make an interesting way of 
processing control voltages.


I was also thinking of doing a module that would produce:

Y = +/-Ax^3 +/-Bx^2 +/- Cx

It can be easily done using three AD633, a summer and three opamps set up 
as an adjustable attenuator with both positive and negative gain (I use a 
similar circuit in my diode shaper)....



At 09:20 PM 1/31/2004 -0600, Ryan Williams wrote:
>I was looking at the analog devices site and I'm came across this IC.
><http://www.analog.com/UploadedFiles/Data_Sheets/737468486AD538_c.pdf>http://www.analog.com/UploadedFiles/Data_Sheets/737468486AD538_c.pdf
>
>AD538. It's a realtime analog computational unit with the transfer function:
>Vout = Vy*(Vz/Vx)^m
>Vy, Vz, and Vx are inputs and m is chosen with resistors. m can range from 
>1/5 to 5.
>
>I thought this might make an interesting module but I'm not quite sure how 
>to go about using it for audio.  I wonder if anyone has thought of 
>building something similar? After looking around I found the MOTM 
>wavewarper which seems to do exactly this. I wonder if it uses the same chip.
>
>this IC costs about $35 but I figure if it sounds cool then it'd be worth it.
>
>-Ryan

         -Jim
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