GATE EC 2020 Set 1 Q20 — Data Converters

A $4$-bit weighted-resistor DAC with inputs $b_{3}, b_{2}, b_{1}$, and $b_{0}$ (MSB to LSB) is designed using an ideal opamp, as shown below. The switches are closed when the corresponding input bits are logic ' $l$ ' and open otherwise. When the input $b_{3} b_{2} b_{1} b_{0}$ changes from $1110$ to $1101$, the magnitude of the change in the …

A $10$-bit analog-to-digital converter (ADC) has a sampling frequency of $1\: \mathrm{MHz}$ and a full scale voltage of $3.3 \: \mathrm{V}$. For an input sinusoidal signal with frequency $500 \: \mathrm{kHz}$ , the maximum SNR (in $\mathrm{dB}$ , rounded off to two decimal places) and the data rate (in $\mathrm{Mbps}$) at the output of the ADC …

​​​​​A full scale sinusoidal signal is applied to a $10$ -bit $\mathrm{ADC}$. The fundamental signal component in the $\mathrm{ADC}$ output has a normalized power of $1 \mathrm{~W}$, and the total noise and distortion normalized power is $10 \mu \mathrm{W}$. The effective number of bits (rounded off to the nearest integer) of the $\mathrm{ADC}$ …

The signal-to-noise ratio $\mathrm{SNR}$ of an $\mathrm{ADC}$ with a full-scale sinusoidal input is given to be $61.96 \mathrm{~dB}$. The resolution of the $\mathrm{ADC}$ is_____________bits (rounded off to the nearest integer).

A sample and hold circuit is implemented using a resistive switch and a capacitor with a time constant of $1 \; \mu \mathrm{s}$. The time for the sampling switch to stay closed to charge a capacitor adequately to a full scale voltage of $1 \mathrm{~V}$ with $12$-bit accuracy is ___________ $\mu \mathrm{s}$ (rounded off to two decimal places).

An $8$-bit unipolar (all analog output values are positive) digital-to-analog converter $\text{(DAC)}$ has a full-scale voltage range from $0\; V$ to $7.68\:V$. If the digital input code is $10010110$ (the leftmost bit is $\text{MSB}$), then the analog output voltage of the $\text{DAC}$ (rounded off to one decimal place) is ___________ $V$.