R-2R LADDER CONVERTER

Figure shows a 4-bit R-2R ladderD/Aconverter,which contains a reference voltage source, a set of four switches, two resistors per bit, and an op amp. The analog output voltage can be shown to be

V_o = - V_ref (b₀ × 2^-1 + b₁ × 2^-2 +···+ b_n-1 × 2^-n )

Because only two resistor values (R and 2R) are used, the R-2R ladder converter networks are relatively simple tomanufacture, fast, practical, and reliable. The commercially available AD558, which is an 8-bit R-2R D/A converter, is an example.