Transistors as control gates and floating gates

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Quick Questions

Shade in the A or B circle for each question.

1. Which part of a flash memory cell traps electrical charge to store a bit?

A The floating gate

B The control gate

2. What does the control gate do in a flash memory cell?

A Permanently stores the data as a magnetic pattern

B Controls whether charge is moved into or out of the floating gate

3. How does a flash cell store one of its two bit values?

A Charge is trapped in the floating gate

B A tiny pit is burned into the surface

4. A cell has no charge in its floating gate. What does this stand for?

A The cell is broken and cannot store data

B The other bit value to the one stored by trapped charge

5. What happens to the charge in the floating gate when the power is turned off?

A It stays trapped, so the data is kept

B It drains away, so the data is lost

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1control gate		AIt is the floating gate that traps the charge. The control gate only controls the transistor by applying voltage.
2floating gate		BThe part of a flash transistor that receives the voltage used to write, read or erase the bit stored in the cell
3Trapped charge in the floating gate stands for one bit value, and no charge stands for the other		Ccharge trapped = one value; no charge = other value
4The charge stays in the floating gate when power is off, so flash memory is non-volatile		DThe part of a flash transistor that traps electrical charge so that the cell can hold a bit value
5The control gate traps the charge that stores the bit		EFlash memory is non-volatile. The trapped charge stays in the floating gate when power is off, so the data is kept.
6When power is off, the floating gate loses its charge and the data is erased		Fpower off -> charge stays -> data kept

Definitions

floating gate transistor

Fill in the Blanks

Complete each line of code by filling in the missing parts.

The ________ gate traps the charge

The _______ gate is used to read or write

Trapped charge = one bit value __ charge = the other bit value

Charge stays in the cell when power is ___

A cell is a __________ with two gates

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A gates = control, power

B IF charge is trapped THEN

C bit = 0

D ELSE bit = 1

Question 2

A power = OFF

B floating gate loses charge

C bit stays stored

Question 3

A cell stores 1 bit

B transistor has 3 gates

C control + floating gate

Question 4

A to store a 0:

B control gate sends charge

C floating gate drains it

Question 5

A // trapped charge = 0

B // no charge = 1

C IF floating gate is full THEN

D bit = 1

Answer Key

Transistors as control gates and floating gates

Section A: Quick Questions

A — The floating gate

B — Controls whether charge is moved into or out of the floating gate

A — Charge is trapped in the floating gate

B — The other bit value to the one stored by trapped charge

A — It stays trapped, so the data is kept

Section B: Match the Pairs

control gate → The part of a flash transistor that receives the voltage used to write, read or erase the bit stored in the cell

floating gate → The part of a flash transistor that traps electrical charge so that the cell can hold a bit value

Trapped charge in the floating gate stands for one bit value, and no charge stands for the other → charge trapped = one value; no charge = other value

The charge stays in the floating gate when power is off, so flash memory is non-volatile → power off -> charge stays -> data kept

The control gate traps the charge that stores the bit → It is the floating gate that traps the charge. The control gate only controls the transistor by applying voltage.

When power is off, the floating gate loses its charge and the data is erased → Flash memory is non-volatile. The trapped charge stays in the floating gate when power is off, so the data is kept.

Section C: Definitions

floating gate transistor — A flash memory cell: a transistor with a control gate and a floating gate that traps charge for one bit value and none for the other, so the bit stays stored when power is off.

Section D: Fill in the Blanks

The floating gate traps the charge

The control gate is used to read or write

Trapped charge = one bit value
No charge = the other bit value

Charge stays in the cell when power is off

A cell is a transistor with two gates

Section E: Spot the Error

A — A flash memory transistor has two gates: a control gate and a floating gate. There is no 'power' gate. Line 1 should be gates = control, floating.

B — The floating gate is insulated, so trapped charge stays there even when the power is off. It does not lose the charge. The line should be floating gate keeps charge.

B — A flash memory transistor has exactly two gates: the control gate and the floating gate. Line 2 should say 2 gates.

C — To store a 0 the floating gate must trap the charge. If it drained the charge, nothing would be stored. Line 3 should be floating gate traps it.

C — The comments say that no charge means 1. The condition for bit = 1 must therefore be an empty floating gate, not a full one. Line 3 should be IF floating gate is empty THEN.