Dr. Hassan Eldib Power Amplifiers • To deliver power to the load efficiently • To deliver a large current to a small load resistance e.g. audio speaker; or to deliver a large voltage to a large load resistance e.g. switching power supply; EC 339 – Electronics 2 – Spring 2017-2018 – Lecture 6 4
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Dr. Hassan Eldib
Power Amplifiers
• To deliver power to the load efficiently
• To deliver a large current to a small load resistance e.g. audio speaker; or to deliver a large voltage to a large load resistance e.g. switching power supply;
Dr. Hassan Eldib 7EC 339 – Electronics 2 – Spring 2017-2018 – Lecture 6
Class A Power Efficiency
Note:
Class A power amplifier has the lowest efficiency. 75% of power is lost. This low efficiency may be due the collector current is non-zero all of the time even when the input signal is zero.
Dr. Hassan Eldib
Class B Operation
• Consists of complementary pair electronic devices.
• One conducts for one half cycle of the input signal and the other conducts for another half of the input signal.
Dr. Hassan Eldib 13EC 339 – Electronics 2 – Spring 2017-2018 – Lecture 6
Dr. Hassan Eldib
Outline
• Introducing the Operational Amplifier (Op-amp) by providing applications:
1. Pulse width modulator
2. Buffer (voltage follower)
3. Non-inverting amplifier
4. Inverting amplifier
5. Summing amplifier
6. Subtracting amplifier
7. Multi-stage (cascade) amplifier
• You are required to write down all calculation written on the white board. In the exam, you are required to be able to replicate the same analysis methodology on different circuits.
• Due to large op-amp gain (A), a small difference between the input voltages results in a very large amplified output voltage.– The output voltage is limited by
supply voltages
• Functions as a comparator, if NO feedback present in op-amp circuit– If V+>V- , Vout = HVS