# Digital circuit question help.

#### Mymla

May 4, 2015
37

(a) For a Sixteen bit converter calculate the expected digital output word given the following inputs. You may assume that Vref is 5V.

(i) 2.3V

(ii) 3.65V

(iii) 4.6V

(b) A 16 bit digital to analogue converter with a voltage reference of 5V has the following digital hex words applied to its input. Calculate the expected voltage output.

(i) 23F4

(ii) 1574

(iii) E357

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
For the first question, can you tell me the range of input voltages and the expected output at these two voltages?

#### Mymla

May 4, 2015
37
I can't sorry those questions are exactly as I was given them. I have no idea how to calculate them

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Ok, the questions I asked require a basic understanding of what an A-D converter does, and all the other required information is in the question.

You need to go back and revise what you have been taught or perhaps do a little research. Is there any suggested reading that you may have skipped?

#### Mymla

May 4, 2015
37
The professor didn't include many of the notes so I can't go back for it. Is there any resource online I can find to help me with it?

#### Mymla

May 4, 2015
37
(Vin/Vref) * 2^12

= (2.3/5)*2^16

= (2.3/5)* 65536

= 30146.56

Am I on the right track?

Also is the secod part the same but in reverse?

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Almost... I assume the 2^12 was a typo.

And while there are 65536 values, one of those is 0, so what is the max value? And can you have fractional values?

And finally, yes, the second question is the first in reverse.

#### Herschel Peeler

Feb 21, 2016
401

(a) For a Sixteen bit converter calculate the expected digital output word given the following inputs. You may assume that Vref is 5V.

(i) 2.3V

(ii) 3.65V

(iii) 4.6V

(b) A 16 bit digital to analogue converter with a voltage reference of 5V has the following digital hex words applied to its input. Calculate the expected voltage output.

(i) 23F4

(ii) 1574

(iii) E357

ai - The most significant bit has a value of 2.5 V. Since this is more than the 2.3 Volts the most significant bit is "0". The next bit has a value of 1.25 Volts. So this bit is a "1". Subtract 1.25 V from the 2.3 V, and continue.

bi - 23F4 = 0010001111110100, right? Again MSB is "0" so the answer is less than 2.5 V, Next is "0" so less than 1.25 V. Next is a "1" so we tally up 0.625. Continue ...

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