RF Design Tutorials:<br>10-Step Design Process for 10W GaN Power AmplifIER in Class E Configuration: Challenges

Power Amplifier Introduction:

The two main characteristics of Gan Devices are high output power density compared to GaAs and higher impedance compared to GaAs.

The two main characteristics of Gan Devices are high output power density compared to GaAs and higher impedance compared to GaAs.
Another advantage is the higher voltage capability of the GaN Devices, leading to higher efficiency, consequently resulting in power savings and reduced costs of cooling of the systems,

A GaN power conversion system supports advanced computing applications such as machine learning and artificial intelligence that require higher power conversion than traditional silicon-based power electronics. Compared to conventional silicon-based power electronics, GaN technology runs at higher efficiency, has a higher power density, and is smaller and lighter. As a result, data center operators can reduce energy consumption, reduce cooling requirements, and lower costs. Recent advances in GaN technology have improved electric vehicle charging systems, enabling faster and more efficient charging. GaN also offers compact and efficient designs in wireless charging applications. As a result, GaN technology is being integrated into various industries besides data centers. In consumer electronics, GaN technology is transforming the design and performance of chargers for smartphones and laptops, making them smaller and more efficient. This allows for faster charging times and reduces the overall size of the chargers, making them more portable and convenient for users. Additionally, GaN’s efficiency contributes to longer battery life and less heat generation in these devices.

A major design requirement in PA design is how efficiently PA converts DC power to RF output power. Efficiency varies depending upon class of operation, from A-E.

GaN advantages: GaN transistors evolved from GaAs (gallium arsenide) prototypes. GaN offers numerous strengths:

1. An operating voltage greater than 100 volts (over-voltage breakdown).

2. High operating temperatures with temperatures over 150°C in the channel

With an increased power density (5 to 30 W/mm).

3. Long-lasting and crack-proof material

It is always a good idea to go through the datasheet for the power amplifier that is to be built using the CGH40010F device from Cree Device, a 10-watt device from DC-6 GHz, providing a small signal gain of 16 dB at 2 GHz Setting up the specifications of the power amplifier is the first step in a good design. 

From the data sheet, we also infer the power added efficiency (PAE) of 65% or more for PSAT, which is less than drain efficiency normally. Curious learners can learn the difference between the two efficiecies from the cadence resource blog. 



DC IV characteristics are the first step in simulation analysis for power amplifier design. I have used FET Curve Tracer from the Insert, Template button. Then I connected my device, CLF, from the library of the components that I already uploaded using this brilliant tutorial from Anurag.

A careful selection for the drain bias values is the double the value they have given in the data sheet; for example, for CGH40010F, the max drain voltage is 28V, the RF Expert Anurag in the video has taken 70V, almost double or a bit more than that, while in my design, I have used the CLF3H series, and this recommends a maximum drain voltage of 50V and VGs = -8V. So we can take anything from a double to a higher value of the maximum recommended value for drain value. 

When we hit the simulate button for this simulation, it will give us a range of values of bias point form that we can select based on our requirements for the output power requirements and efficiency requirements. We choose an operating point using markers that gives us the required Pout in dBm, >40 dBm for example, and small signal gain, >14 dB, e.g., and large signal gain, 12 dB for example, and noise figure less than 3 dB or less than 1-2 dB if it is the Low Noise Amplifier Design.