Download Cambridge Checkpoints 2012 HSC Physics Chapter 8 Age of

Cambridge Checkpoints 2012 HSC Physics
Chapter 8 Age of Silicon Study Notes
Age of Silicon
Voltage dividers

Are used in many applications to either reduce the amount of voltage in a secondary circuit or as a sensor
when used with thermistors and LDRs. The sum of the voltage must be equal to the voltage supplied. The
ratio of the resistance is equal to the ratio of the voltages.
Transducers
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Are devices that can be affected by the environment and can affect the environment. In circuits there are
two types of transducers, input transducers and output transducers.
Input transducers are affected by the environment and are usually used as sensors. Examples of input
transducers are LDRs, Thermistors and Microphones.
Output transducers affect the environment and turn electrical energy in to other forms. Examples of output
transducers are speakers and LEDs.
Thermistors

Change their resistance based on the surrounding temperature. If they increase their resistance as the
temperature increases then they are said to have a positive temperature coefficient, the most common
thermistors have a negative temperature coefficient and therefore reduce their resistance as the temperature
is increased.
LDRs

Change their resistance based on the surrounding light intensity. If they increase their resistance as the
temperature increases then they are said to have a positive temperature coefficient, the most common
thermistors have a negative temperature coefficient and therefore reduce their resistance as the temperature
is increased.
LEDs
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Light Emitting Diodes draw very little current and are much more efficient at producing light when compared
to conventional lighting.
They have a fixed voltage and need to have an accompanying resistor in series to ensure it does not
receive too much current or voltage.
Internal structure of an LED is made up from a p-type and n-type material. When an external voltage
is applied to the LED, the electrons in the n-type are able to move towards the holes in the p-type material.
There is a difference in the energy of the electrons as they move into the holes and this extra energy is
emitted as light.
Analogue and Digital

An analogue signal represents a continuous quantity and can therefore have any value. A digital signal
represents a binary value and therefore has only one of two values. Analogue signals are affected by
noise when transmitted over great distances because the signal to noise ratio would increase. Analogue is
also affected by noise when undergoing amplification as the noise is also amplified. Since digital is either
off or on, it is not as easily affected by noise.
Logic gates
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Are elementary building blocks of electronic circuits. Types of logic gates include: AND, OR, NOT, NOR,
NAND, XOR.
Half adders are made by using an AND with a XOR gate, see the diagram below:
Full adders are made by using an AND and XOR gates, see the diagram below:
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Cambridge Checkpoints 2012 HSC Physics
Chapter 8 Age of Silicon Study Notes
Transistors

Can be used as an electronic switch. Once the Base — Emitter voltage exceeds 0.7 V the switch is turned on.
When used in conjunction with a thermistor or LDR this can be used as a temperature or light controlling
device.
Amplifiers
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
Properties of an amplifier are:
infinite input resistance so it does not load the source circuit.
Zero output resistance so the amplifier output is not dependent on the load.
Infinite / very high differential gain
The gain of an ideal amplifier is the ratio of the output voltage divided by input voltage. It is also the gradient
of a Vout – V in graph.
𝐴0 =





𝑉𝑜𝑢𝑡
𝑉𝑖𝑛
Operational amplifier is a component of a typical amplifier
Open-loop gain is when there is no feedback of the output to the input. The gain under these conditions
is very high and tending towards infinite. A closed-loop gain is much lower and is determined by the
resistors in the circuit feedback loop.
An amplifier will only provide linear amplification if the input stays within the linear regions of the amplifier.
If the input exceeds this then the output will be clipped at the maximum and minimum values.
An operational amplifier can be used to make an inverting amplifier by connecting it in the following way:
The gain of an inverting amplifier can be found using the formula below:
𝑅𝑓
𝑉𝑜𝑢𝑡
=−
𝑉𝑖𝑛
𝑅𝑖

Two input resistors can be used to produce a summing amplifier using the following circuit:
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Cambridge Checkpoints 2012 HSC Physics
Chapter 8 Age of Silicon Study Notes
The output voltage for the summing amplifier can be calculated using the following:
𝑉1 𝑉2
𝑉𝑛
𝑉𝑜𝑢𝑡 = −𝑅𝑓 ( + … = + )
𝑅1 𝑅2
𝑅𝑛
Otherwise you can calculate the Vout for each Vin and add them together.
Future computing

The speed of computers has doubled roughly every 18 months, this cannot continue into the future
indefinitely as the reason the computers have increased their speed is the size of the components has
decreased, the smaller distance allows the information to travel across the computer quicker. One limitation is
that the components can only go so small; they are limited to the size of the atom.
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