Hello,
I did not expect that my first participation here is going to be something about R-2R. Sorry for that!
The question that bothers me about this R-2R ladder circuit is about its linearity. Is it linear? Many documents say that it is linear. But, i think it is not. Look, i know that we can apply the superposition technique in it, but this does not mean that it is TOTALLY LINEAR.
Here it is my proof:
I made 4 bits R-2R ladder for a DAC system. I supplied it with 9 volts battery. The calculation shows that i should expect 8.4 if all the bits are on. Okay, suppose now i want instead a supply of 9.3. Can't I just subtract the 0.3 from the output to get the same as the 9.0's output? What do you think?
In fact, i tried that, and i got the same but it was off by 0.025.
and in another case working with different bits .. it was off by 0.1 volts.
It is supposed to be non linear because the output is always expressed as Vin/(2^n) = Vout where n is the bit we work with. So, if we add 0.3 to Vin, it does not make sense to get Vout+0.3 ???? so why is it linear ?
I did not expect that my first participation here is going to be something about R-2R. Sorry for that!
The question that bothers me about this R-2R ladder circuit is about its linearity. Is it linear? Many documents say that it is linear. But, i think it is not. Look, i know that we can apply the superposition technique in it, but this does not mean that it is TOTALLY LINEAR.
Here it is my proof:
I made 4 bits R-2R ladder for a DAC system. I supplied it with 9 volts battery. The calculation shows that i should expect 8.4 if all the bits are on. Okay, suppose now i want instead a supply of 9.3. Can't I just subtract the 0.3 from the output to get the same as the 9.0's output? What do you think?
In fact, i tried that, and i got the same but it was off by 0.025.
and in another case working with different bits .. it was off by 0.1 volts.
It is supposed to be non linear because the output is always expressed as Vin/(2^n) = Vout where n is the bit we work with. So, if we add 0.3 to Vin, it does not make sense to get Vout+0.3 ???? so why is it linear ?