EEPROM storage physics – is the floating-gate MOSFET the bit-cell, with charge retained on the floating gate for 10+ years unless electrically removed?

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Understanding how nonvolatile memories store information helps explain retention and endurance specs. EEPROMs and Flash use a floating-gate transistor to store charge, which alters the cell’s threshold voltage and thereby encodes a bit. The statement summarizes this behavior and typical retention times.


Given Data / Assumptions:

  • Bit cell is a floating-gate MOSFET.
  • Charge storage modifies threshold to represent 0/1.
  • Typical retention guarantees exceed 10 years under nominal conditions.


Concept / Approach:
The floating gate is insulated by oxide, so injected electrons remain trapped for long periods. Reading senses the threshold shift; erasing/programming adds or removes charge via tunneling. Unless an erase/program pulse or high-temperature stress accelerates leakage, charge remains for many years, aligning with datasheet retention specs.


Step-by-Step Solution:

1) Identify the storage mechanism: charge on an isolated conductor (floating gate).2) Correlate charge with threshold voltage and logic state.3) Note retention: oxide isolation yields multi-year stability (often 10–20+ years).4) Conclude the description is accurate.


Verification / Alternative check:
Vendor specifications specify retention at temperature (for example, 10 years at 85 C or longer at room temperature). Field-programmable microcontrollers store firmware in Flash for device lifetimes without continuous power.


Why Other Options Are Wrong:
The mechanism is common to EEPROM and Flash; continuous power is not required for charge retention; claiming hours contradicts practice.


Common Pitfalls:
Confusing retention (data persistence) with endurance (cycle count). Retention is long even as endurance limits write/erase frequency.


Final Answer:
Correct

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