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Re: [AVR-Chat] PWM

2006-01-10 by Roy E. Burrage

It actually is a divider, Micah. Each leg of the R2R ladder divides the output current by 2.


REB


Micah Stevens wrote:
Why? This isn't a divider circuit. I think I see what you're getting at, but 
I'm not sure I'm buying it. 

-Micah 

On Monday 09 January 2006 1:57 pm, Jim Wagner wrote:
  
 Sorry, but wrong about the tolerance!

 Each successive leg has half the tolerance contribution of
 the leg just above it in the ladder. With 1% resistors, the
 over-all tolerance will be in the 3-4% range.

 What may be more critical is monotonicity, especially the
 step going from 0x7f to 0x80 (in an 8-bit) DAC.

 An R-2R DAC also relies on the on-resistance of the FETs in
 the logic output circuit.

 Jim
    
  

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