Brush up on the theory before designing a high power Class‐E amplifier: Page 8 of 15

June 29, 2016 // By Alfio Scuto, Roberto Cammarata, ST Microelectronics
The most promising switched-mode PA for RF applications, among the several types available, is the Class-E for several reasons: high efficiency, simplicity of the load network, and a satisfying performance even with a non-optimal drive signal.

In simulation, we implemented Equation 20, Equation 21, and Equation 22, with capacitors and inductors lossless and loaded quality factor QL (resonant load) chosen as high as 10. The measurement equations include the conditions when the switch voltage and its voltage derivative is zero just before the switch is turned ON. In order to reach the steady-state condition and check the Class-E conditions, 20 periods were considered.

Figure 5: Transient to reach the steady-state.

Figure 6: Zoom of transient at 20th period.

To evaluate the relationship between the device’s RDS(on) and the required R_load required from theoretical Class-E, we performed a switching voltage simulation at different coefficient factors: R_load_factor defined as ratio between the RDS(on) and the R_load (Figure 6).


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