Simple Binary-Weighted and R/2R Ladder DAC

A basic 4-bit computerized to-simple converter that is developed from a digitally controlled switch (74HC4066), an arrangement of twofold weighted resistors, and an operational speaker. The essential thought is to make an altering intensifier circuit whose pick up is controlled by changing the info resistance Rin. The 74HC4066 and the resistors together go about as a digitally controlled Rin that can interpretation of one of 16 conceivable qualities. (You can think about the 74HC4066 and resistor mix as a digitally controlled current source. Each new parallel code connected to the contributions of the 74HC4066 creates another discrete current level that is summed by RF to give another discrete yield voltage level.) We pick scaled resistor estimations of R, R/2, R/4, and R/8 to give Rin discrete qualities that are similarly divided. To locate every single conceivable estimation of Rin, we utilize the recipe gave. This equation resembles the old resistors-in-parallel recipe, yet we should prohibit those resistors which are not chose by the computerized input code-that is the thing that the coefficients A through D are for (a coefficient is either 1 or 0, contingent upon the advanced information).


Presently, to locate the simple yield voltage, we just utilize Vout = −Vin (RF/Rin)- the expression utilized for the modifying speaker demonstrates what we get when we set Vin = −5 V, R = 100 kω, and RF = 20 kω, and take all conceivable information codes. The parallel weighted DAC appeared above is restricted in determination (4-bit, 16 simple levels). To twofold the determination (make a 8-bit DAC), you may think to include another 74HC4066 and R/16, R/32, R/64, and R/128 resistors. In principle, this works; in all actuality, it doesn’t. The issue with this approach is that when we achieve the R/128 resistor, we should locate a 0.78125-kω resistor, accepting R = 100 kω. Accepting we can discover or build a proportional resistor arrange for R/128, we’re still in a bad position on the grounds that the resiliences of these resistors will spoil things. This scaled-resistor approach gets to be illogical when we manage resolutions of more than a couple of bits.