Memory technologies — relative bit-cell size In general, which technology has the smallest bit-cell area and which has the largest, when comparing common integrated memory types?

Introduction / Context:
Integrated memories implement one logical bit using a “cell.” Different memory families use different devices for the cell (for example, a transistor-capacitor in DRAM or multiple transistors in SRAM). Cell design directly affects density (bits per mm^2), cost, power, and speed. This question compares typical, mainstream implementations used in digital systems.

Given Data / Assumptions:

• We are comparing mainstream mask ROM, DRAM, Flash/EEPROM, and SRAM bit-cell sizes on silicon.
• “Smallest” means highest density; “largest” means lowest density for a single stored bit.
• Conventional read-only mask ROM is implemented with the fewest devices per bit.

Concept / Approach:

Mask ROM encodes data as the presence or absence of a device or connection, achieving extremely compact cells. DRAM uses 1 transistor + 1 capacitor per bit, also very dense but larger than simple ROM geometry. Nonvolatile Flash/EEPROM cells require special structures (floating gates, tunneling oxides), so area is moderate. SRAM typically needs 6 or more transistors per bit for static storage, making it the least dense (largest cell area).

Step-by-Step Solution:

Verification / Alternative check:

Textbooks and vendor datasheets consistently report SRAM density far below DRAM/ROM due to multi-transistor cells, while mask ROM is historically the densest because it eliminates write circuitry entirely.

Why Other Options Are Wrong:

• EEPROMs, Flash: these are denser than SRAM but not denser than mask ROM.
• SRAM, mask ROM: reverses the true order.
• DRAM, PROM: DRAM is not the smallest compared to mask ROM; “PROM” is a family term and not necessarily the largest.

Common Pitfalls:

• Confusing access speed (often fastest for SRAM) with density (lowest for SRAM).
• Assuming all ROMs have identical density; mask-programmed ROMs are typically most compact.

Final Answer:

mask ROM, SRAM