Edited By : Engr. Muhammad Muizz bin Mohd Nawawi

Edited By : Engr. Muhammad Muizz bin Mohd Nawawi

In an electronic circuit, a combination of high voltage (+5V) and low voltage (0V) is usually used to represent a binary number. For example, a binary number 1010 is represented by Weighting 2 3 2 2 2 1 2 0 Binary Digit 1 0 1 0 State +5V 0V +5V 0V DACs are electronic circuits that convert digital, (usually binary) signals (for example, 1000100) to analog electrical quantities (usually voltage) directly related to the digitally encoded input number.

DIGITAL TO ANALOGUE CONVETE

egister DACs are used in many other applications, such as voice synthesizers, automatic test system, and process control actuator. In addition, they allow computers to communicate with the real (analog) world. Input Binary Number Voltage Switch esistive Summing Network Amplifier Analog Voltage Output

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Binary Weighted esistor Ii f = 2 4 8 V o MSB LSB -V EF 10

Binary Weighted esistor Ii f = Most Significant Bit 2 4 8 V o Least Significant Bit -V EF 11

Binary Weighted esistor Most Significant Bit SET CLEAED -V EF Least Significant Bit ( 1 1 1 1 ) 2 = ( 15 ) 10 12

Binary Weighted esistor Weighted esistors based on bit Ii f = educes current by a factor of 2 for each bit MSB 2 4 8 V o LSB -V EF 13

14 esult: B i = Value of Bit i B B B B V I EF 8 4 2 0 1 2 3 8 4 2 0 1 2 3 B B B B V I V EF f OUT Binary Weighted esistor

Binary Weighted esistor More Generally: V OUT B i = Value of Bit i n = Number of Bits B i VEF n 2 i V Digital EF 1 Value esolution 15

The circuit in above figure is a digital to analog converter circuit of resistors 4-bit binary weights. We can calculate the resistor values using the weight of binary numbers. For example, the most high-value resistor (150 kω = 1) is a digital input resistor, the smallest bit (least significant bit), and the values of the other resistor are: 2 = 1 = 150K 2 1 2 = 75 kω Bit 21 3 = 1 = 150K 2 2 4 4 = 1 = 150K 2 3 8 = 37.5 kω Bit 2 2 = 18.75 kω Bit 2 3

Now we will analyze the circuit to get the output, Vout for a number of digital input. i. Binary input = 1000. 1 = 150 kω, F = 20 kω, The gain of the voltage (AV) = F / 1 = 0.133 Vout = Vref x AV = 3 V X 0.133 = 0.4V ii. Binary input = 0110 2 = 75 kω, 3 = 37.5 kω, T = (2 3 partially parallel) = 25 kω. AV = 20 kω /25 kω = 0.8, Vout = Vref x AV = 3 V X 0.8 = 2.4V or in = Vout = Vref and F resistance. Vout can found by substituting the resistance values of the total amount of resistance when certain binary input. In summary we can see the resulting output is shown in Table below.

Table 1 Decimal Binary Input D C B A V out (V) 0 0 0 0 0 0 1 0 0 0 1 0.4 2 0 0 1 0 0.8 3 0 0 1 1 1.2 4 0 1 0 0 1.6 5 0 1 0 1 2.0 6 0 1 1 0 2.4 7 0 1 1 1 2.8 8 1 0 0 0 3.2 9 1 0 0 1 3.6 10 1 0 1 0 4.0 11 1 0 1 1 4.4 12 1 1 0 0 4.8 13 1 1 0 1 5.2 14 1 1 1 0 5.6 15 1 1 1 1 6.0

This circuit is different from binary up a resistor DAC circuit because it only uses two resistor values, and 2. Disadvantage that we can see is too much of the resistor to be provided. For example, if 12-bit DAC with resistor value MSB (most significant bit), then it is 1kΩ resistor will exceed 2MΩ LSB.

One method of analyzing this circuit is to find a resolution for this circuit. The resolution [full-scale resolution] for this circuit is the Vref / 3 ie by setting input 012 = 110. Full scale output of the circuit is by setting the input will produce 112 = 310 = Vout. Then the general expression for the circuit is Vout = where n = number of bits and B in = digital input converted to decimal numbers.

a) From figure a below, when input 01 2 = 1 10, Vout = b) The input 10 2, the circuit is as figure b From figure b, when input 10 2 = 2 10, Vout = c) The input 11 2, the circuit is as figure c. From figure c, when input 11 2 = 3 10, Vout = We can get the general equation for output as: V ref 2 3V 4 ref f f V ref 4 f V 0ut = V 00 + V 01 + V 10 + V 11 = 0 + V ref f V 0ut = 0 1 2 3 4 V ref 4 f + V ref 2 f + 3V 4 ref f In conclusion, from what we have to prove from the analysis on the circuit, the output Vout = V ref n 2 converted to decimal. f B in,where n = number of bits and B in = binary input that has been

Masukan D C B A Jadual 5.2 keluaran,v OUT V OUT = V 2 ref n 0 0 0 0 0 0 0 0 1 0.3125 0 0 1 0 0.6250 0 0 1 1 0.9375 0 1 0 0 1.2500 0 1 0 1 1.5625 0 1 1 0 1.8750 0 1 1 1 2.1875 1 0 0 0 2.5000 1 0 0 1 2.8125 1 0 1 0 3.1250 1 0 1 1 3.4375 1 1 0 0 3.75 1 1 0 1 4.0625 1 1 1 0 4.375 1 1 1 1 4.6875 f B 5 16 in = B in B 4 in 2 5

Defined as the smallest change achieved in the analog output as a result of changes in digital input. esolution can be expressed in two cases, either the voltage or Ampere and also percent also known as the step size. Maximum output voltage.

Digital to analog converter 10-bit with step size 10 mv. Search for full-scale voltage and percent resolution.

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