Q.With a neat diagram explain the working of 4 bit R-2R ladder network DAC.

An R-2R ladder DAC converts a 4-bit binary input into a proportional analog voltage using only two resistor values, R and 2R, with each bit switched between the reference voltage and ground, and a buffer op-amp at the output. …

[!TLDR]

An R-2R ladder DAC uses just two resistor values (R and 2R) and per-bit switches to $V_{ref}$/ground; each successive bit's contribution halves (8, 4, 2, 1 V for $V_{ref}=16\,\mathrm{V}$), and a buffer op-amp outputs a voltage proportional to the binary input.

Circuit: A digital-to-analog converter (DAC) converts a digital (binary) input into a proportional analog output. The 4-bit R-2R ladder DAC uses a ladder network made of only two resistor values, $R$ and $2R$ (for example $1\,\mathrm{k}\Omega$ and $2\,\mathrm{k}\Omega$). The four binary inputs are switches $S_4$ (MSB) to $S_1$ (LSB), each of which can be connected either to $V_{ref} = 16\,\mathrm{V}$ (logic 1) or to $0\,\mathrm{V}$/ground (logic 0). The ladder output is fed to a buffer op-amp (voltage follower) which supplies the analog output $V_{out}$ without loading the ladder.

Working:

• When all switches are at 0 V, the output $V_{out} = 0\,\mathrm{V}$.
• Because of the repeated R-2R halving action, connecting only one switch to $V_{ref}$ gives a definite fraction of $V_{ref}$ at the output:

• When several switches are at logic 1, the superposition principle applies: each active bit adds its own weight, so the output is the sum of the individual contributions. For example $(1010)_2 = 8 + 2 = 10\,\mathrm{V}$. …