Question 3 (15pts) a. What is the minimum voltage a 10-bit ADC can measure if th

Question

Question 3 (15pts) a. What is the minimum voltage a 10-bit ADC can measure if the ADC can take V 2.5V and VreH= 0V? Select the closest answer. (5pts) i. 2mv ii. 20mV iii. 200mV Briefly explain why the flash ADC has a higher conversion speed than the sigma-delta ADC. (5pts) maximum frequency of the input signal which can be sensed by this ADC? (Spts) (Hint: whot is the Nyquist theory?) c. A 12-bit ADC has a sampling rate of 250kS/s (- kilo sample per second), what would be the lem Glwer as helow:

Explanation / Answer

Flash analog-to-digital converters, also known as parallel ADCs, are the fastest way to convert an analog signal to a digital signal. Flash ADCs are ideal for applications requiring very large bandwidth, but they consume more power than other ADC architectures and are generally limited to 8-bit resolution.

Flash vs. Sigma-Delta ADCs

Flash ADCs do not compete with a sigma-delta architecture because currently the achievable conversion rates differ by up to two orders of magnitude. The sigma-delta architecture is suitable for applications with much lower bandwidth, typically less than 1MHz, and with resolutions in the 12- to 24-bit range. Sigma-delta converters are capable of the highest resolution possible in ADCs. They require simpler anti-alias filters (if needed) to bandlimit the signal prior to conversion.

Sigma-delta ADCs trade speed for resolution by oversampling, followed by filtering to reduce noise. However, these devices are not always efficient for multichannel applications. This architecture can be implemented by using sampled data filters, also known as modulators, or continuous-time filters. For higher frequency conversion rates the continuous-time architecture is potentially capable of reaching conversion rates in the hundreds of Msps range with low resolution of 6 to 8 bits. This approach is still in the early research and development stage and offers competition to flash alternatives in the lower conversion rate range.

Another interesting use of a flash ADC is as a building block inside a sigma-delta circuit to increase the conversion rate of the ADC.

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