Four calculation problems related to ADC

[benji_styler]

Im wondering if someone could give me some information/resources on ADC's so that i can complete the following questions. I havent got a great deal of knowledge on the subject as i studied it a while back and am recoving it. Any help/ideas would be much appriciated.

1.) A 3-bit successive approximation ADC has a full-scale input of 7V. Explain the steps in the conversion process showing how the 3-bit digital output is arrived at when the analougue input is 5.5V

2.) A 4-bit ADC has a full-scale input of 10.5V. What is the 4-bit binary output when the input is 4.0V?

3.) An ADC has a conversion time of 1us. It is used t sample and digitally store frequencies of up to 50kHz. how many samples is this ADC able to do one complete cycle of 50kHz?

4.) A microphone is used to record music. The maximum output voltage over the whle performance is 300mV. the music i to be digitised and stored using an ADC with a full-scale input of 2.5V. What voltage amplification is required between microphone output and ADC input?

 

[sivani_vs]

Re: ADC's?

two signals
1.start of conversion
2. endof conversion

connect the analog input to the adc. apply thge SC signal low. ADC will start converting the data .

the analog input of the adc is given as one input to the comperator. the second input is the ref. signal. it starts comparing if the analog input is greater than the ref.signal the MSB bit of the SCR is set to 1this process continues until the last bit is to be set.
after the last bit set the EOC signal goes high. And the OE ( output enable ) goes high. then the output lines of the ADC are enable. OE line is narmally low.

 

[aland]

Re: ADC's?

1)

2.) 4.0/10.5 * 15 (4bits is 0 to 15) -> 0101 (5)

3.) 50kHz has a period of 1/50000 = 20uS. therefore 20 x 1uS samples could be made per cycle. Nyquist requires at least 2 samples per cycle.

4.) None is necessary, but amplification up to 2.5v/0.3v (8.33) will yield better resolution of the signal.