What does a photodiode characteristic curve plot, and what general trends does it show?

It plots photocurrent against reverse bias voltage for different light intensities. Photocurrent increases with light intensity and remains relatively constant across a range of reverse bias voltages.

Why does photocurrent remain approximately constant over a range of reverse bias voltages on a photodiode characteristic curve?

Once sufficient reverse bias is applied, essentially all photo-generated carriers are swept across the depletion region, so further increases in reverse voltage do not significantly increase the current.

What is dark current in a photodiode?

Dark current is the small reverse leakage current that flows through a photodiode when no light is incident on it.

How does dark current appear on a photodiode characteristic curve?

It appears as the baseline current level when the photodiode is in complete darkness.

What does a spectral response curve of a photodiode show?

It plots the responsivity or sensitivity of the photodiode against the wavelength of incident light.

Over what approximate wavelength range do silicon photodiodes respond, and where is their peak sensitivity?

Silicon photodiodes typically respond from approximately 400 nm to 1100 nm, with peak sensitivity around 900 nm.

AQA A-Level Physics 7408

Measurements and Their Errors

Topic overview Use of SI units and their prefixes Limitation of physical measurements Estimation of physical quantities

Particles and Radiation

Topic overview Constituents of the atom Stable and unstable nuclei Particles, antiparticles and photons Particle interactions Classification of particles Quarks and antiquarks Applications of conservation laws The photoelectric effect Collisions of electrons with atoms Energy levels and photon emission Wave-particle duality

Waves

Topic overview Progressive waves Longitudinal and transverse waves Principle of superposition of waves and formation of stationary waves Interference Diffraction Refraction at a plane surface

Mechanics and Materials

Topic overview Scalars and vectors Moments Motion along a straight line Projectile motion Newton's laws of motion Momentum Work, energy and power Conservation of energy Bulk properties of solids The Young modulus

Electricity

Topic overview Basics of electricity Current–voltage characteristics Resistivity Circuits Potential divider Electromotive force and internal resistance

Further Mechanics and Thermal Physics

Topic overview Circular motion Simple harmonic motion (SHM)Simple harmonic systems Forced vibrations and resonance Thermal energy transfer Ideal gases Molecular kinetic theory model

Fields and Their Consequences

Topic overview Fields Newton's law Gravitational field strength Gravitational potential Orbits of planets and satellites Coulomb's law Electric field strength Electric potential Capacitance Parallel plate capacitor Energy stored by a capacitor Capacitor charge and discharge Magnetic flux density Moving charges in a magnetic field Magnetic flux and flux linkage Electromagnetic induction Alternating currents Transformers

Nuclear Physics

Topic overview Rutherford scattering α, β and γ radiation Radioactive decay Nuclear instability Nuclear radius Mass and energy Induced fission Safety aspects

AstrophysicsOptional topic

Topic overview Astronomical telescope consisting of two converging lenses Reflecting telescopes Single dish radio telescopes, I-R, U-V and X-ray telescopes Advantages of large diameter telescopes Classification by luminosity Absolute magnitude, M Classification by temperature, black-body radiation Principles of the use of stellar spectral classes The Hertzsprung-Russell (HR) diagram Supernovae, neutron stars and black holes Doppler effect Hubble's law Quasars Detection of exoplanets

Medical PhysicsOptional topic

Engineering PhysicsOptional topic

Topic overview Concept of moment of inertia Rotational kinetic energy Rotational motion Torque and angular acceleration Angular momentum Work and power First law of thermodynamics Non-flow processes The p–V diagram Engine cycles Second Law and engines Reversed heat engines

Turning Points in PhysicsOptional topic

Topic overview Cathode rays Thermionic emission of electrons Specific charge of the electron Principle of Millikan's determination of the electronic charge, e Newton's corpuscular theory of light Significance of Young's double slits experiment Electromagnetic waves The discovery of photoelectricity Wave–particle duality Electron microscopes The Michelson-Morley experiment Einstein's theory of special relativity Time dilation Length contraction Relativistic mass and energy

ElectronicsOptional topic

Topic overview MOSFET (metal-oxide semiconducting field-effect transistor)Zener diode Photodiode Hall effect sensor Difference between analogue and digital signals LC resonance filters The ideal operational amplifier Inverting amplifier configuration Non-inverting amplifier configuration Summing amplifier configuration Real operational amplifiers Combinational logic Sequential logic Astables Principles of communication systems Transmission media Time-division multiplexing Amplitude (AM) and frequency modulation (FM) techniques

Electronics

Photodiode

4 things to know
Paper 3, section B

Overview

Responsivity, photo-conductive mode, and detecting particles with a scintillator.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

How is responsivity defined, and what units does it take?

Numbers

How does photocurrent vary with light intensity, and why does reverse bias improve response?

Process

How does a scintillator and photodiode detect an atomic particle, and what does the pulse amplitude tell you?

Key term

For what application is photovoltaic mode typically used?

Questions from this subtopic

Each one with the model answer underneath.

1
What does a photodiode characteristic curve plot, and what general trends does it show?
Model answer
It plots photocurrent against reverse bias voltage for different light intensities. Photocurrent increases with light intensity and remains relatively constant across a range of reverse bias voltages.
2
Why does photocurrent remain approximately constant over a range of reverse bias voltages on a photodiode characteristic curve?
Model answer
Once sufficient reverse bias is applied, essentially all photo-generated carriers are swept across the depletion region, so further increases in reverse voltage do not significantly increase the current.
3
What is dark current in a photodiode?
Model answer
Dark current is the small reverse leakage current that flows through a photodiode when no light is incident on it.
4
How does dark current appear on a photodiode characteristic curve?
Model answer
It appears as the baseline current level when the photodiode is in complete darkness.
5
What does a spectral response curve of a photodiode show?
Model answer
It plots the responsivity or sensitivity of the photodiode against the wavelength of incident light.
6
Over what approximate wavelength range do silicon photodiodes respond, and where is their peak sensitivity?
Model answer
Silicon photodiodes typically respond from approximately 400 nm to 1100 nm, with peak sensitivity around 900 nm.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book

2Open book

3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Measurements and Their Errors

Particles and Radiation

Waves

Mechanics and Materials

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Q is .

positivenegativezero

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AP = 4πr²σT⁴.

BThe surface area of a spherical star is 4πr².

CP₁/P₂ = (r₁²/r₂²) × (T₁⁴/T₂⁴).

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Speed means rate of change of distance.

TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Electronics, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a month See how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.