Question

please make a research report on this

ADC en DAC algorithms (type of algorithms and a brief functional description (few sentences) with pro’s and con’s, at least 3 algorithms))

Answer 1

DAC

DIGITAL TO ANALOG CONVERTER

Types

1.Summing Amplifier

Since digital to analog conversion is simply a weighted sum of the binary input, a circuit called a summing amplifier is used.

This is basically an op-amp amplifier with multiple resistors connected to one input. The junction where the resistors meet is called the summing junction or the virtual ground. The binary input goes into the resistors and the analog output is obtained on the output of the op-amp.

What makes this circuit work is the resistors – each resistor has to be carefully chosen and matched in order to obtain an accurate analog output. The more bits you have, the more different values of resistors you need – and this is not always practical. The limitations can be overcome by using the next method.

2. R2R Ladder

This is the simplest type of DAC and needs only two resistor values arranged in a ladder. You can think of this as a somewhat complex voltage divider, though the math is quite complex.

The binary input goes into the 2R resistors and the output is obtained at the bottom of the ladder.

3.PWM DAC

This is the type of DAC that most of us have used without even knowing it!

The popular Arduino microcontroller has the capability to output analog signals using a PWM signal. On the outset the PWM signal looks like a binary waveform with only high and low peaks with a variable duty cycle (ratio of on time to time period).

However, this is intended to be used with a RC filter to convert the PWM signal into a voltage value by filtering out the AC component and leaving behind the DC component. The voltage output is proportional to the duty cycle of the input – the higher the duty cycle the greater the output voltage of the filter.

ADC

Analog to digital converter

Types

1.Flash ADC

Flash converters have a resistive ladder that divides the reference voltage in 2N equal parts. For each part, a comparator compares the input signal with the voltage supplied by that part of the resistive ladder. The output of all the comparators is like a thermometer: the higher the input value, more comparators have their outputs high from bottom to top. A dedicated component called "Priority Encoder" translates this gauge into a binary code, which corresponds to the position of the last comparator with high output, counting from the bottom up.

2.The priority encoder

The Priority Encoder has to find the position of the last comparator with high output, starting from the bottom. That means that it should find the position where neighboring comparators have different outputs (all below have output high and all above have output low). That can be simply done by XORing the outputs of neighboring comparators and feeding their outputs to a digital encoder. Only one XOR has its output active and the encoder will translate that position into a binary representation. If there are 2^N comparators, the encoder outputs a N-bit number. Very fast and converts easily. Consumes a lot of power