Digital electronics general questions

Hi Everyone,

I am appearing for an interview in a company where the requirement is of Digital Electronics. I would like to know if there is a site where I could get some good digital electronics questions for preparation for the interview. Some of the questions asked in the previous interview.

1) design a circuit to implement the function y=2^x x input, y output
2) charging and discjarging of a capacitor connected to a CMOS inverter
3) Desing a circuit that produces an ouput that is just like the clock pulse but the Time period is three times the clock pulse.
4) questions regarding setup and hold time, metastability.

Could any one please let me know where I could get similar questions (and answers) for practise. Also could anyone tell me the solution for the 3rd question.

Thanks,
Chan999

3) Clock period that is three times of the original clock "pulse" is difficult to make in digital circuit. I think you mean 3 times of the clock cycle...
Hint: Use two 2-bit counters, one driven by positive edge of the clock, another driven by the negative edge.

Hi lostinxlation,

To clarify question3, when we use a binary ripple counter, and denote the output as A3A2A1A0. then the timeperiod of A0 is twice that of the clock. That of A1 is 4times that of clock. So we need to design a ckt that produces an output that has time period 3 times that of clock.
Question 4, setup, hold time and propagation dealy is given, we have to calculate the max frequency of the clock that can be aplplied.
Also could tell me where I could get similar questions.

Thanks a lot,
Chan999

to answer question 4,
The condition for setup is T(clock-Q) + T(combo) < T(clock_period) - T(setup)

substitute the values for T(clock-q), T(combo) and T(setup) to find the clock period and hence the frequency.

normally the frequency of operation does not depend on hold