2. Given the partial NMOS EPROM encoder shown, where Y is some select line, determine the values of the output data lines D2D1D0 when Y = 1.

  1. D2=0 D1=0 D0=0
  2. D2=1 D1=0 D0=1
  3. D2=1 D1=1 D0=0
  4. D2=0 D1=1 D0=0
  5. D2=0 D1=0 D0=1

4 is CORRECT. Since the floating gate associated with T1 is charged negatively, T1 cannot turn on and conduct to Ground when Y = 1. Therefore T1 is OFF and D1 will be high through the top R-transistor. Alternatively, the floating gates associated with T2 and T0 remain uncharged and will allow these transistors to turn on. Thus T2 and T0 will be ON, grounding D2 and D0 when Y = 1.

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