Class C and D Power Amplifiers — Lesson - 2

This lesson covers the the different classes of amplifiers, including class C, and D, and their construction and operation. The lesson also explains the concept of RF choke and DC block in the context of MOSFET. It further elaborates on the calculation of power consumption and power delivery in these circuits, which helps in determining their efficiency. For instance, the lesson provides a detailed explanation of how class B and class C amplifiers work, their efficiency, and the power delivered to the load.

Video Highlights

00:25 - General picture of a MOSFET amplifying a voltage, RF choke and a DC blocking capacitor
06:02 - power delivered to the load and the efficiency of amplifiers
17:16 - Relationship between Rantenna, Imax and power supply
24:11 - Relationship between Class B and Class C amplifier
33:28 - Detailed mathematical explanation of the efficiency of class C amplifiers

Key Takeaways

- Power amplifiers are categorized into different classes, including A, B, C, and D, each having unique characteristics and applications.
- An RF choke is an inductor that acts as a short circuit for DC, while a DC block is a capacitor that prevents DC from passing through but allows other frequencies.
- The power consumption of a circuit is calculated by multiplying the average current (Iavg) by the supply voltage (VDD).
- The efficiency of an amplifier is determined by the power delivered to the load at the desired frequency.
- Class B amplifiers have an efficiency of around 77%, while class C amplifiers can achieve higher efficiencies by conducting for lesser durations of time.