Physics Circuits Assignment Help

Physics Circuits Assignment Help

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Physics Circuits Assignment Help

Draw a cross-section of a CMOS inverter in a twin-well process. Explain how and why the wells are biased.

Why? Channel

1. Does a higher level of metal typically have a higher resistance per unit length than a lower level metal?

Why or why not?

No. Physics: l/w higher ->larger->lower resistance.

Why? Longer wire, I/O, Power.

1. Does a lower level of metal have higher lateral (adjacent) capacitance per unit length than a higher level metal? Assume that the wires are minimum width and shielded on both sides at minimum spacing.

No. higher metal is taller.

1. Why was copper introduced as an on-chip interconnect? What metal did it replace? What challenges needed to be overcome for copper to be used in integrated circuits?

Lower resistance.

1. What does Harris mean by the zipper in a data-path circuit? Give an example of a data-path circuit?  What are the distinguishing characteristics of a data-path layout

Adder

1. What is the logical effort for an XNOR gate in standard CMOS (assume that inputs are available in both true and complemented form). . Draw a transistor-level schematic with the sizes to justify your answer.

1. (GRAD ONLY)

What is a typical value for σ for threshold voltage?  Name 2 other sources of variation in integrated circuits from the paper.  Limit yourself to those with time scale less than 1 msec.

Sigma = ~50mV

Vth=400mV

Temperature

Vdd not stable, not solid supply

Noise

Vth

1. (GRAD ONLY)

Give an approximate value for the energy-optimal value of Vdd from the Sub-threshold paper.  How does this value change with the activity factor?

Near threshold

3. Consider the following Voltage Transfer Characteristic for an inverter (35 points for 558, 40 for 658)

1. In which region are both transistors in saturation?   5 pts

C 

1. In which region is the short circuit current maximized? 5 pts

C

1. How will increasing the load capacitance impact the VTC? 5pts

No impact. In DC analysis, no impact.

1. Show how decreasing the NMOS transistor length (e.g due to process variation) will modify the Transfer Characteristic. 10pts
2. The curve slide left.

1. Modify the VTC to provide a better high noise margin NMh   10pts

1. GRAD ONLY:   Indicate the  regions of operation for the P and N transistors  in A,B,C,D,E  assuming that we are operating in sub-threshold mode   5 pts
2. (35 points for 558, 40 for 658)

3. Draw a schematic for the following layout.  Label A,S,B and Z.  20 pts

Lucky for you this circuit only uses one metal layer. 

	Inputs A, S and B are labeled on metal1/poly contacts Output Z is on the right on metal 1

Multiplexor

1. Indicate the transistor widths and lengths on the schematics, assuming a 45nm feature size (HINT: assume the contact width and spacing are at the minimum feature size) 5 pts.

1. What logic function does this circuit perform?   5 pts

1. Comment on the P/N ratio? 5 pts.

1. GRAD ONLY: Note that all of the polysilicon lines are straight.  Why is this desirable in advanced technologies?  5 pts.

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