Chapter 5 : Signal conversion

Question 1

What can be said about the number of comparators and the number of output bits on a flash converter?

Answer 1

As the number of output bits increase, so does the number of comparators

Question 2

What is the priority encoder made of?

Answer 2

Number of logic gates

Question 3

How would you calculate the voltage drop across each resistor on a flash encoder

Answer 3

Vref/number of resistors

Question 4

What does the overflow indicator do in a flash encoder

Answer 4

Indicates that the analogue input has exceeded the range

Question 5

How would you calculate the number of comparators needed for a flash convertor

Answer 5

2^n
n=bits

Question 6

What is the advantage of a flash ADC

Answer 6

It’s speed; its conversion time from AC to binary is 100ns

Question 7

What is the disadvantage of a flash ADC

Answer 7

Cost-Due to the number of comparators and the complexity of the circuit

Question 8

Compare Flash ADC to Digital ramp ADC

Answer 8

Flash ADC-faster conversion
Flash ADC more complicated
Digital ramp conversion time depends on AC input-smaller input, smaller conversion time

Question 9

What’s the point of ADC

Answer 9

Avoids adding noise to the AC signal.
The quality depends on the number of bits and the sampling rate

Question 10

How does the DAC work?

Answer 10

Output increases as the binary input increases

Question 11

Draw a DAC based on a summing amp

Answer 11

See notes