The inverted R-2R ladder DAC is used to overcome the disadvantages of current varying in a weighted register DAC, such as large power dissipation, heating, and nonlinearity in current. It works by interchanging the most and least significant bits and connecting the binary inputs to switches that route to either ground or the inverting input of an op-amp virtual ground. This keeps the current flowing through the resistors constant, divides the current equally at each node since resistances are equal on both sides, and produces a constant voltage at each node.

1. INVERTED R-2R
LADDER DAC

2. Why we use inverted r-2r ladder DAC?
 Current flowing in weighted register DAC varying.
 It causes large power dissipation.
 It produces heating and causes non linearity in current flowing through
resistors.
 To overcome these disadvantage we use inverted r-2r ladder DAC.

3. Circuit Diagram

4. Working
 MSB and LSB are interchanged.
 Binary input datas are connected to switch either to ground or to the inverting input
terminal of the op-amp which is at the virtual ground.
 0 - switch connected to ground.
 1 - switch connected to virtual ground.
 The current flowing through resistors constant.
 In each node,current dvides equally.
 Because the resistance value is equal in botha right and left side of each node.
 Thus the constant current implies constant voltage across each node.

5. To find Io :

7. THANK YOU