What are the four types of resistors?
- carbon composition
- carbon film
- metal film
- wire-wound
Explain the constructional features of a carbon composition resistor, as well as some advantages and disadvantages.
- made of a mixture of finely ground carbon (conductor) and an insulating mixture (insulator)
- the ratio of carbon : insulator gives resistance values
- good for short but large overloads (lots of bulky resistive material)
- bad frequency response (noisy over 10MHz due to capacitive/inductive properties)
Explain the constructional features of a carbon film resistor, as well as some advantages and disadvantages.
- the general resistors one would use for breadboards
- a helical track through the resistive material (thus exposing the conductive carbon) creates the resistance (changing pitch of helix changes the resistance)
- good: very close tolerances
- bad: resistance drifts with temperature
Explain the constructional features of metal film resistors, as well as some advantages and disadvantages.
- similar to carbon film except for the resistive material used
- good: don’t drift as much with temperature; good for high-freq. applications; less expensive
What are wire-wound resistors, and why are they used?
Literally some wire wound around an insulating object. They dissipate more heat and are thus used in high-power applications.
What type of capacitor has the best frequency range/response?
Ceramic capacitors (work at anything below 100MHz)
What type of capacitor has the highest capacitance, and what are some of its features?
Tantalum (electrolytic)
Tantalum metal foil with solid semi-conductor in between
Up to 2mF capacitance!!
How can supercapacitors store so much charge? Draw a diagram showing where positive and negative ions are.
- plates are soaked in charcoal, making them able to attract and absorb more electroncs (effectively a larger surface area, which increases capacitance)
- because of a thin dialetric between the two plates, the distance affecting capacitane is far smaller
Why is there a need for balancing networks when charging supercapacitors, and what might this look like?
Supercapacitors vary signficantly in their internal capacitance - it is quite common to find one cell with a capacitance of 100F, and another with 130F! If connected in series across a voltage source, they would both charge to different amounts.
To prevent this, one must use an appropriately size resistor network to ensure the current supplied is the same.
How do variable capacitors work?
Moving plates over each other - when they are fully over each other it is the maximum capacitance.
What is a unijunction transistor?
A p-n junction with three pins, used in timing circuits.
What is a zener diode, and how is it used?
A diode used in reverse-biased position that conducts in one direction but doesn’t in the other. Its claim to fame, however, is that when reverse biased, it blocks anything below a certain volage (Zener voltage), and allows anything exceeding that.
What is a varactor diode?
A diode that acts as a capacitor when reverse biased.
What is a Siliconm Controlled Rectifier, or Thyristor?
A device that may be switched from a non-conductive state to a conductive one when applying current to the gate. Instead of amplifying it (like a transistor), it simply makes the cathoe - anode conductive.
What is a Triac?
Conducts current in both direction and is triggered in to conduction by a negative or positive pulse.
What impact may low temperatures have on electronic components?
- any electrolyte (capacitor, batteries, etc…) may freeze and fail
- some silicon and germanium-doped materials don’t function well, as they depend on thermal excitation for charge carriers to exist
- any water vapour or condensation build up may cause cracking when it turns to ice
What impact may high temperatures have on electronic devices?
- the increased thermal load may exceed the limits of any heat sink and cause failure
- very fast thermal overload can ruin solder joints
What is a known thermal weak point in electronic devices, and what are some ways to mitigate this?
Solder joints
Use gold wires and special solder alloys (e.g. Gold-Tin)
What are ‘tin whiskers’, and how can they affect electronic circuits?
Metal whisker formations from solder.
They can bridge across terminal strips, connectors, or PCB tracks, thus ruining components.
What are ‘thermal joint compounds’, and how may they be used?
Special heat conductive pastes used between mating surfaces - e.g. heatsink and GPU.
What is an ‘isolating kit’, and why are they useful?
Often, the voltage out pin of an IC is connected to the actual frame of the IC. This means the frame is live! To prevent this, one may purchase an ‘isolating kit’, which is a thin piece of dialetric (mica) to be placed between the IC and the heatsink.
What is this connector, and what is it used for?
It’s a PS/2 connector, developed by IBM to connect mice and keyboard to a computer.
What are the two types of communucation ‘ports’, or protocols?
Serial and parallel
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Reticulation & distribution (AS3000, Energex standards)0
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Electronics18
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Control Systems27
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Logic Families20
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Transistor Amplifiers8
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Module 5 - Microprocessor Operation12
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Data transmission (networking & cryptography)36
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Operating Systems (process, storage, memory & device management)12
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Module 1: Components27
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Module 3: PCB Design & Manufacture4
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Module 1: Semiconductors17
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Module 2: Logic Circuits29
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Module 3: Amplifiers33
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Module 4: Op-amps16
