Figure 1 shows a simplified structure of an N-channel enhancement mode MOSFET - AQA - A-Level Physics - Question 1 - 2021 - Paper 8

In typical MOSFET configurations using it as a simple switch, the source terminal is connected directly to 0 V.

To find the minimum value of $V_{GS}$ required to operate the lamp at full power, we first calculate the current $I$:

Using the formula for power, $P = I^2 R$, we rearrange to find $I$:
I = rac{P}{R} = rac{0.65 ext{ W}}{154 ext{ Ω}} o I ext{ is approximately } 0.00423 ext{ A} (or 4.23 ext{ mA}).

Next, we refer to Figure 2 and interpolate where $I_{DS}$ matches this value across the curves for varying $V_{GS}$. This leads us to conclude that for the lamp to operate at its full power, the minimum $V_{GS}$ needed is approximately 3.4 V.

The current consumption in standby mode calculated as follows:
$I = 8.5 imes 10^9 imes 10^{-6} imes 8 ext{ s}.$ This indicates a significant amount of current when millions of MOSFETs are in operation.

Regarding battery life, we know that a fully charged battery of 1 A allows 3600 C of charge. Hence, for a device with a 3110 mAh capacity:

• The calculation shows that the battery can sustain power and operational timings for the CPU effectively for varying periods up to approximately 12 hours under average use.
• Each MOSFET’s specified current consumption informs design considerations in mobile phones that rely on efficiency and conductance, emphasizing the relevance of low I_DSS levels and managing their combined load.