Digital Abstraction - Interview Question

1. The behavior of a 1-input, 1-output device is measured by hooking a voltage source to its input and measuring the voltage at the output for several different input voltages:
   
   We're interested in whether this device can serve as a legal combinational device that obeys the static discipline. For this device, obeying the static discipline means that

   if V_IN <= V_IL then V_{OUT >=} V_OH, and
   if V_IN >= V_IH then V_{OUT <=} V_OL.

   • Can one chose a V_OL of 0V for this device? Explain.
   • What's the smallest V_OL one can choose and still have the device obey the static discipline? Explain.
   • Assuming that we want to have 0.5V noise margins for both "0" and "1" values, what are appropriate voltage levels for V_OL, V_IL, V_IH, and V_OH so that the device obeys the static discipline. Hint: there are many possible choices, just choose one that obeys the constraints listed above.
   • Assuming that we want to have 0.5V noise margins for both "0" and "1" values, what is the largest possible voltage level for V_OL that still results in a device that obeys the static discipline?
   • Assuming that we want to have equal noise margins for both "0" and "1" values, what is the largest noise margin we can achieve with this device and still obey the static discipline?
   

Difficulty: Medium