Basics of electrical engineering and electronics

1. Ahmed Elwali
BME 7022 & ECE 4610
Biomedical Instrumentation
and signal processing
TUTORIAL

2. Ahmed Elwali
BME 7022 & ECE 4610
Objectives
· Ohm’s law.
· Parallel and series connections.
· Voltage and current dividers.
· Referencing, open circuit, and short circuit.
· Using KCL and KVL techniques for electrical circuit analysis.
· Diode and half wave rectification, and Zener diode.
· Frequency spectrum.
· Capacitor in electrical circuits.
· Different types of filters (4 types).
· OPAMP operation and applications.

3. Ahmed Elwali
BME 7022 & ECE 4610
What’s the main Difference between?
AC Vs DC
Signals

4. Ahmed Elwali
BME 7022 & ECE 4610
AC Vs DC
Alternating current (AC) Direct current (DC)
Current flow’s direction changes Current flow’s direction doesn’t change
Outlet voltage (120V, 60Hz) Canada Batteries (1.5V, 3V, etc.)
Voltage

5. Ahmed Elwali
BME 7022 & ECE 4610
The main three measurements in any
electrical circuit
Voltage (V)
Impedance (Z)
Resistance (R)
Current (I)
Ohm’s law

6. Ahmed Elwali
BME 7022 & ECE 4610
What’s the main Difference between?
Passive Vs Active
Electrical components

7. Ahmed Elwali
BME 7022 & ECE 4610
Passive Vs Active
Active components require to be powered to work, and some of them
are used to amplify signals

8. Ahmed Elwali
BME 7022 & ECE 4610
Parallel and series connections
I
What’s the current I ?
Simplify

9. Ahmed Elwali
BME 7022 & ECE 4610
Parallel and series connections
Series connection (same current)
Summation
Rtotal = R1 + R2 + ….. + Rn
Parallel connection (same voltage)
Reciprocal summation
𝟏
𝐑𝐭𝐨𝐭𝐚𝐥
=
𝟏
𝐑 𝟏
+
𝟏
𝐑 𝟐
+ … +
𝟏
𝐑 𝐧
Only two resistances
Rtotal =
𝐑 𝟏
. 𝐑𝟐
𝐑 𝟏
+𝐑𝟐
N equal resistances
Rtotal =
𝐑
𝐍

10. Ahmed Elwali
BME 7022 & ECE 4610
What’s the current I ?
I
Simplify

11. Ahmed Elwali
BME 7022 & ECE 4610
Voltage and Current dividers
Voltage signal attenuation or creating
reference voltage.
Vout = Vin .
𝒁 𝟐
𝒁 𝟏
+𝒛 𝟐
Current signal attenuation

12. Ahmed Elwali
BME 7022 & ECE 4610
Referencing (common/GND)
Open circuit (OC)
Short circuit (SC)

13. Ahmed Elwali
BME 7022 & ECE 4610
What’s the output voltage?
Vout = ??

14. Ahmed Elwali
BME 7022 & ECE 4610
What if we need all circuit’s measurements??
I
I1 I2

15. Ahmed Elwali
BME 7022 & ECE 4610
KVL and KCL for electrical circuit analysis
Kirchhoff’s voltage law (KVL)
The algebraic sum of voltages in a closed loop
equals Zero
𝒌=𝟏
𝒏
𝑽 𝒌 = 𝟎
Kirchhoff’s current law (KCL)
The algebraic sum of currents at a point (node)
equals Zero
𝒌=𝟏
𝒏
𝑰 𝒌 = 𝟎
Based on the principle of conservation of energy

16. Ahmed Elwali
BME 7022 & ECE 4610
KVL and KCL for electrical circuit analysis
Use all the available tools and knowledge to
solve any problem.
Circuit Analysis procedure:
1 - Define the currents & signs.
2 - Define voltages (if required).
3 – Define the nodes.
4 - Define the closed loops (direction).
5 – Apply KCL and KVL.
6 – Construct the equations and solve them.
Example

17. Ahmed Elwali
BME 7022 & ECE 4610
Solve this circuit using KCL and KVL

18. Ahmed Elwali
BME 7022 & ECE 4610
Diode and Zener diode

19. Ahmed Elwali
BME 7022 & ECE 4610
Frequency spectrum
Fourier series
Frequency Spectrum
𝝎 = 𝟐𝝅𝒇
(f)

20. Ahmed Elwali
BME 7022 & ECE 4610
Capacitors and RC circuits
* Capacitor work
* Capacitor at DC circuits (Transient and steady state)
𝝎 =
𝟏
𝝉=𝑹𝑪
= 𝟐𝝅𝒇 @ 𝑽𝒄 = 𝟎. 𝟔𝟑𝟓 𝑿 𝑽𝒐; (𝟑 − 𝟓) 𝝉 for steady state
* Capacitor at AC circuits (OC and SC)
X𝒄 =
𝟏
𝝎𝒄
𝐼 𝑐 = 𝐶
𝑑𝑉 𝑐
𝑑𝑡

21. Ahmed Elwali
BME 7022 & ECE 4610
Low and High pass filters (RC circuits)
Low pass filter
𝝎 𝒄 =
𝟏
𝝉=𝑹𝑪
= 𝟐𝝅𝒇𝒄@ Vo = 0.707 Vin or -3db
Filter order
High pass filter
𝝎 𝒄 =
𝟏
𝝉=𝑹𝑪
= 𝟐𝝅𝒇𝒄@ Vo = 0.707 Vin or -3db
Filter order

22. Ahmed Elwali
BME 7022 & ECE 4610
Bandpass filter and Bandstop filter
How to construct each of them using low and high pass filters circuits??

23. Ahmed Elwali
BME 7022 & ECE 4610
Basic Twin-T Notch filter

24. Ahmed Elwali
BME 7022 & ECE 4610
Draw the expected spectrum of the
following RC circuit
Vin Vout

25. Ahmed Elwali
BME 7022 & ECE 4610
Operational amplifier (OPAMP)
MA741

26. Ahmed Elwali
BME 7022 & ECE 4610
Op-Amp characteristics
Differential input
Very high input impedance
Very low output impedance
Very high open loop gain (empirical)
Very low input current
Saturation voltage is the supply voltage

27. Ahmed Elwali
BME 7022 & ECE 4610
Op-Amp operation
Open loop amplifier - Closed loop amplifier
Used as comparator (open loop)
◦ Open loop gain is very high
Closed loop:
◦ Positive feedback (used for oscillators, creating signals)
◦ Negative feedback
Vin

28. Ahmed Elwali
BME 7022 & ECE 4610
Negative feedback (closed loop)
Using the op-amp as buffer (voltage transferring between two circuits)
(high Zin and low Zout)
Proof:
Vout = AOL (V+ - V-)  Vout = Vin
Network
Load
Load

29. Ahmed Elwali
BME 7022 & ECE 4610
Inverting and non-inverting amplifier
Working in the non-saturated mode with impedances (resistances) lower than Zin of the OP-amp,
we can assume the following:
◦ Very High Zin means iin is very low ~= 0
◦ V+ = V-
Current here is zero
Inverting Amplifier Non-Inverting Amplifier

30. Ahmed Elwali
BME 7022 & ECE 4610
Summation and integrator

31. Ahmed Elwali
BME 7022 & ECE 4610

32. Ahmed Elwali
BME 7022 & ECE 4610