A-Level AQA Physics Electromotive Force & Internal Resistance: Figure 1 shows a simplified stru

Question

Figure 1 shows a simplified structure of an N-channel enhancement mode MOSFET.

State the name of the part shown in this MOSFET structure that causes the input resistance to be very large.

Which terminal of the MOSFET is connected directly to 0 V when it is used as a simple switch?

Tick (✓) one box.

drain  
gate  
source

Figure 2 shows how the drain–source current $I_{DS}$ of the MOSFET varies with drain–source voltage $V_{DS}$ for a range of gate–source voltages $V_{GS}$.

The MOSFET is used as a simple switch in a filament lamp circuit.
The circuit uses power rails of 12 V and 0 V.
The resistance of the lamp is 154 Ω when operating at its full power of 0.65 W.

Deduce the minimum value of $V_{GS}$ needed for the lamp to operate at full power.

Figure 3 shows an individual MOSFET. The drain–source leakage current $I_{DS}$ for this MOSFET is about 10 nA.

Figure 4 shows a microchip where millions of MOSFETs are combined to enable complex processes to be carried out on one chip.

A mobile phone has a central processing unit (CPU) which uses a microchip similar to the one in Figure 4.

Table 1 shows the technical specification for the mobile phone.

Number of transistors in the CPU  8.5 × 10⁹  
Battery capacity  3110 mAh  
Phone time available on stand-by from one full charge ≈ 12 hours

A fully charged battery with a capacity of 1 A allows 3600 C of charge to flow through it before it is fully discharged.

The loss value for each MOSFET used in the mobile phone CPU must be estimated from the individual MOSFET shown in Figure 3.

Discuss, using the data provided, the relevant information.

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

Worked Solution & Example Answer:Figure 1 shows a simplified structure of an N-channel enhancement mode MOSFET - AQA - A-Level Physics - Question 1 - 2021 - Paper 8

State the name of the part shown in this MOSFET structure that causes the input resistance to be very large.

Which terminal of the MOSFET is connected directly to 0 V when it is used as a simple switch?

Deduce the minimum value of $V_{GS}$ needed for the lamp to operate at full power.

Discuss, using the data provided, the relevant information.

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