R-2R DAC

-

  R-2R DAC


This is Combinational Logic Circuit

The R-2R Digital-to-Analogue Converter, or DAC, is a data converter that converts a digital binary number into an analogue output signal proportionate to the digital number's value using two precision resistors.

R-2R DAC Circuit with Four Zero (LOW) Inputs




(RF/RIN)*VIN is the output voltage of an inverting operational amplifier. If we set RF equal to R, RF = R = 1, and R is connected to ground (0V), there is no VIN voltage value (VIN = 0), hence the output voltage is (1/1)*0 = 0 volts.
As a result, the output voltage of a 4-bit R-2R DAC with four grounded inputs (LOW) will be “zero” volts, and a 4-bit digital input of 0000 will yield an analogue output of 0 volts.

So, if we link input bit VA HIGH to +5 volts, what happens? What is the R-2R ladder network's equivalent resistive value, as well as the op-output amp's voltage?

R-2R DAC with Input VB




 




The output voltage, VOUT, is computed at 625mV, which is one-eighth (1/8th) the value of the +5V input (5/0.625 = 8) voltage, with input VB HIGH and logic level “1” and all other inputs grounded at logic level “0.”

We can also observe that when only input bit VA is applied, the output voltage is doubled, which is to be expected because the 2nd bit (input) has twice the weighting of the 1st bit.

Let's check what happens if we link input bit VC HIGH to +5 volts and observe what happens to the output voltage.

R-2R DAC with Input VC






The output voltage, VOUT, is computed at 1.25 volts, which is one-quarter (1/4) the value of the +5V input (5/1.25 = 4) voltage, with input VC HIGH and logic level “1” and the remaining input bits at logic level “0.” This voltage is double the output of input bit VB but also four times the value of bit VA, as can be seen.
Because input VC is the third bit, its weighting is double that of the second bit and four times that of the first bit.

Finally, let's look at what occurs when we connect input VD HIGH to +5 volts and observe what happens to the output voltage.




Comments

Post a Comment

Popular posts from this blog

Frequency Divider

-
Image
  Frequency Divider It called as Clock divider That circuit  takes an input signal of a  frequency  and generates an output signal of a frequency Frequency  is the number of occurrences of a repeating event per  unit of time Create Frequency divider using JK Flip Flops  A frequency divider can be constructed from J-K flip-flops by taking the output of one cell to the clock input of the next. The J and K inputs of each flip-flop are set to 1 to produce a toggle at each cycle of the clock input. For each two toggles of the first cell, a toggle is produced in the second cell, so its output is at half the frequency of the first. The output of the fourth cell is 1/16 the clock frequency. The same device is useful as a binary counte r Create & Simulate        
Read more

Multiplexers

-
Image
  Multiplexer (MUX)   MUX is a Combinational Logic Circuit with more than one input line, one output line and more than one select line  It accepts the binary information from several input lines or sources and depending on the set of select lines, a particular input line is routed onto a single output line.  Multiplexer acts as a multiple-input and single-output switch It has only one output and   2n  inputs It identified as digital Switch Types of Multiplexers 1) 2 X 1 MUX                          2) 4 X 1 MUX        3) 8 X 1 MUX     1)    2 X 1 MUX    A 2-to-1 multiplexer consists of two inputs D0 and D1, one select input S and one output Y.  Depending on the select signal, the output is connected to either of the inputs. Since there are two input signals, only two ways are possible to connect the inputs to the outputs, so one select is needed to do these operations. If the select line is low, then the output will be switched to D0 input, whereas if select line is high, then the out
Read more

Demultiplexers

-
Image
De-multiplexer The de-multiplexer is a combinational logic circuit designed to switch one common input line to one of several separate output line. 1 to 4 De-multiplexers
Read more