In a typical EPROM memory cell used for non volatile storage, which type of transistor structure is used inside each cell to store charge and represent data?

Introduction / Context:
This question addresses the internal structure of EPROM memory cells. EPROM stands for erasable programmable read only memory and is a type of non volatile memory that can be programmed electrically and erased with ultraviolet light. Each EPROM cell must hold its state for long periods without power, so it uses a transistor structure capable of storing charge in an isolated region. Understanding this structure gives insight into how non volatile semiconductor memories operate.

Given Data / Assumptions:

We are specifically dealing with EPROM technology, not RAM or EEPROM in general.

Each memory cell must store a bit of information in a non volatile manner.

The storage mechanism relies on charge held in an isolated region that affects transistor conduction.

The question asks which type of transistor structure is used inside each EPROM cell.

Common transistor types include bipolar junction transistors, JFETs, MOSFETs, and more specialized devices.

Concept / Approach:
EPROM cells are built using a special type of MOSFET called a floating gate MOSFET. In this structure, there is a conducting gate completely surrounded by insulating oxide, with no direct electrical connection. Charge can be injected onto or removed from this floating gate using high voltage programming pulses. Once charge is stored on the floating gate, it modifies the threshold voltage of the MOSFET, changing whether the transistor conducts for a given control gate voltage. This change represents the stored bit as a logical one or zero. Because the floating gate is isolated by oxide, the charge remains for a long time, giving the device its non volatile property.

Step-by-Step Solution:
Step 1: Recall that EPROM technology relies on charge stored in an insulated region inside each memory cell transistor.Step 2: Identify the transistor structure that supports a floating gate, namely a MOSFET with an additional isolated gate electrode.Step 3: Recognize that bipolar junction transistors and JFETs do not naturally provide this type of isolated charge storage in standard memory cell designs.Step 4: Examine the options and find the one that mentions a metal oxide semiconductor field effect transistor with a floating gate.Step 5: Select option C, as it accurately describes the transistor used in EPROM cells.

Verification / Alternative check:
Semiconductor memory textbooks and manufacturer application notes describe EPROM cells as based on floating gate MOS transistors. Diagrams typically show two gates: a floating gate embedded in oxide and a control gate above it. Programming injects electrons onto the floating gate, and erasing with ultraviolet light discharges it. These details match the description of a MOSFET with a floating gate. Bipolar transistors, SCRs, and simple diodes cannot provide the same non volatile charge storage mechanism used in EPROM devices, confirming that option C is correct.

Why Other Options Are Wrong:
Option A describes a bipolar junction transistor that is common in analog circuits and logic families like TTL but is not the core element in EPROM cells. Option B mentions a JFET, which has a different gate structure and is not used for charge storage in EPROMs. Option D introduces an SCR, a device used for power control and latching but not for bit storage in EPROM memory arrays. Option E refers to a diode connected pair, which cannot store charge in the required isolated way for non volatile memory.

Common Pitfalls:
Students may think of older bipolar technologies or assume that any transistor can be used to build memory without considering the need for long term charge storage. Another pitfall is to confuse EPROM with simpler ROM technologies that use fusible links or mask programmed connections. To answer correctly, remember that modern EPROM and related flash memories rely on floating gate MOSFET structures for storing information.

Final Answer:
Each EPROM memory cell uses a metal oxide semiconductor field effect transistor MOSFET that has a floating gate for charge storage to implement non volatile data storage.