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Electronic circuits: lecture 1Corresponding book chapters:
- Ch.11: 1-6
- Ch.12: 1-2, 9
Electronics: basics
What are we talking about, when we talk about electronics?
- System:
o Signals that are not electrical go in
o signals become electrical
o signals leave the system and become something different than electrical again
- so systems may often be described simply by: their inputs and outputs and the relationship
between them
Example: microphone > electrical input > audio-amplifier > electrical output > speaker
- there is a input quantity that is sensed and an output quantity that is produced
- sense a quantity from a source (left part)
- process the information
- produce a signal and it goes in to a load
o load: can be a lamp / motor / antenna
- important: there is an interface from the sensor (source) to the system and from the
electrical system to the load
o it can be a voltage or current that goes from the one part (sensor) to the other
(system), but you can also have a varying resistance where you can measure the
resistance
- its very important what you want to senso of a signal source
o do you want to measure the current or voltage that it produces, it makes quite a
difference
o if you made the wrong choice, then you get loss of quality which cannot be repaired
by the system
- “interface errors create damage to the information processing quality beyond repair”
,signals:
- You can have analogue circuits and digital circuits
- Digital circuit:
o discrete in amplitude, but it has different discrete amplitudes > a multi-valued digital
signal
- if you talk about the digital circuit and a digital signal with just zero’s and ones > a binary
signal
key words: an analoguqe signal, a multi-valued digital signal, a binary signal
Shannon’s equation:
- what do you specify for an electronic circuit
- in principle there are only three things that you need to specify to be able to get the proper
design:
𝑆+𝑁
𝐶 = 𝐵 ⋅ ^2 𝑙𝑜𝑔
𝑁
o C: the maximum channel capacity (bits per second)
o Depends on the bandwidth of the signal, B, and the logarithm of the signal to noise
ratio (S & N)
o What you need to give to an electrical engineer:
▪ What the bandwidth is that you want, what the maximum signal level is and
what the noise level is
▪ Distortion (S = maximum signal level)
▪ Noise (N)
▪ Bandwidth (B)
Distortion = repeatable error
- Systematic repeatable
o Clipping
o Crossover distortion
o Harmonic distortion
,Noise: smallest signal you can recognize
Noise = Random, Not repeatable
- You cannot predict it
- Some signals are more resistant to noise than others: like digital binary signal
o But the zero crossing of the signal can be shifted by the noise
- All systems that add power to a signal add noise
- Noise can be (partly) removed from digital signals
Bandwidth = system has a limited speed at which it can react
Systematic repeatable:
- If you look at the voltage across the capacitor
- When you close the switch
- The voltage of the capacitor is not immediately the voltage of the supply voltage, but it
slowly climbs to it > speed limitation
- Fast transients and high frequencies are lost
Imperfections:
- Distortion, what is the largest signal you can have before distortion
- Noise , what is the smallest signal you can have before it disappears in the noise
- Bandwidth, what is the finite speed
Just these three specify the system
Cost factors follow: power, technology, financial cost, etc that are negotiable and compromises
, Sensors: (chapter 12)
- Sensor: converts a physical quantity into an electrical signal, that an electronic system can
use to process further
- The importance for this course:
o Sensor produces some electrical signal, has some electrical property
o We want to properly read that with the electronical circuit
Describing sensor performance: how wo specify the sensor (when is it good and when not)
- range
- resolution
- error
- linearity
- sensitivity
- accuracy
- precision
the performance of the sensor is the minimal spec for the performance of electronic system
- If you get the wrong spec of the sensor, you will get the wrong circuit
Accuracy, precision:
- You have accurate sensors and precise sensors
- Precise sensor = sensor where all the measurements results are close to each other
o B: high precision, not accurate because all the measurements have an offset, but
they are close to each other
▪ Not so much noise, but it might have an off set
o C: best sensor you can have, its accurate and precise
o A: sensor that is neither precise nor accurate
o Precision; tells you something about the noise
o Accuracy: tells you something about the off set that you can tolerate
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