MOSFET

Under Dennard (constant-field) scaling, which statement is correct when dimensions and voltages are each scaled by 1/k?

  1. ACircuit delay becomes 1/k, and power density stays constant
  2. BCircuit delay increases by a factor of k
  3. CPower density increases by a factor of k²
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Answer: A. Circuit delay becomes 1/k, and power density stays constant

Under Dennard scaling, with dimensions and voltages scaled by 1/k and doping by k, the internal field stays constant, delay becomes 1/k and power per device 1/k²; since area also shrinks by 1/k², power density stays constant. Since the mid-2000s, when threshold and supply voltages became hard to lower, this relationship has broken down.

  • A. Correct. Circuits get faster and power density stays constant.
  • B. Smaller dimensions reduce delay (make circuits faster).
  • C. Because voltage is also reduced, power density ideally stays constant.
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More MOSFET questions

  1. Which correctly describes the flat-band voltage of a MOS structure?
  2. In a high-frequency C-V measurement of a MOS capacitor on a p-type substrate, what happens to the capacitance when a large positive gate voltage drives the surface into strong inversion?
  3. In a MOSFET with a very thin gate insulator, what is the effect of the electron distribution in the inversion layer peaking slightly away from the interface?
  4. Which expression appropriately gives the small-signal output resistance ro of a MOSFET in saturation, using the channel-length modulation coefficient λ and drain current ID?
  5. Which is the common condition for "strong inversion" used to define the threshold voltage of a MOSFET? (φF: Fermi potential)