Digital to analog converter Digital to analog converter

Digital to analog converter

Digital to analog converter • Used to convert digital signal in to analog signal • Input is n-bit binary • Output is either voltage or current • Input digital signal is combined with reference voltage to get an analog output

Digital to analog converter TYPES OF DAC • Binary weighted resistor DAC • R-2 R ladder DAC

Binary weighted resistor dac • Operational amplifier is used to sum n binary weighted currents • The binary weighted currents are derived from a reference voltage Vr through current scaling resistors-2 R, 4 R, 8 R……. . 2 n R

Binary weighted resistor dac • The switch positions are controlled by the digital inputs • When the digital input is 1 the corresponding switch is closed • When the digital input is 0 the corresponding switch is open

Binary weighted resistor dac • Operational amplifier is used as summing amplifier • Due to high input impedance of operational amplifier , summing current will flow through feed back resistor Rf

Binary weighted resistor dac • By Kirchhoff's current law, the total current is The analog output voltage is directly proportional to the digital input

R-2 r ladder dac • 1 -representing voltage(Vr) • 0 -representing ground • The ladder network should never be left open circuited • The switch positions d 1, d 2, d 3 corresponds to the binary word 100

R-2 r ladder dac • The output voltage Vo = Vr/2 • The output voltage is proportional to the sum of the weights represented by the switches

R-2 r ladder dac Advantages • High resolution • High accuracy • It requires only two resistors R and 2 R