2022-10-31 21:03 Tags: # Binary Resistor Based DACs ## Basic Circuit Using binary type converters we can make significantly less complex circuits. Binary weighted resistors can be switched to ground or virtual ground The summing node). The voltage across each resistor is the same, so the current becomes binary weighted.  This same current then flows through the feedback resistor. $I_{out}=\sum_{n=0}^{N-1}\frac{I}{2^{N-1}}\cdot 2^n\cdot B_n$ Implementation of the switches is a couple of MOS switches, each switching to either the ground or virtual ground.  ### Advantages - Simple ### Disadvantages - Non-linearity (nasty [Differential Non-linearity](Differential%20Non-linearity.md)) This is because around the code where MSB changes (01111 -> 10000) the change in current should be 1 LSB. However we actually change from all the other LS resistors conducting to just the MS Resistor conducting. This leads to a very accurate match needed. - Very large Resistor ratios (very hard to match) Can be fixed with an [[#R-2R Ladder]] - Area is the same as a resistor string since the $2^N$ resistor will be $2^N$ larger than the LS Resistor. ## R-2R Ladder  Still get a binary weighted set of currents. ### Advantages - Smaller Resistor ratio Easier to match, small area [^1] --- # References [^1]: [vr-4602-wk07-sc02-dacrbin](../../Spaces/University/ELEC4602%20–%20Microelectronics%20Design%20and%20Technology/Lectures/W7/vr-4602-wk07-sc02-dacrbin.mp4)