A very important consideration when operating a power amplifier is its ability to remove the heat generated by the device. Power transistors, like all semiconductors, must remain below their maximum permitted junction temperature. If too much power is dissipated through the transistor, the junction temperature will increase and the component will become damaged. Even if the device is operated below this threshold where damage may occur, the performance will still be negatively impacted due to the heat.
As temperature increases, the amplifier’s gain will decrease and the noise figure will increase. The efficiency of the device will also decrease as most of the potential electrical energy is wasted as heat. One method used to eliminate excess heat and improve the device’s performance is utilizing a heat sink.
Heat sinks are designed for a particular device in order to pull heat from the device to the surrounding medium, such as air or a liquid coolant, as quickly as possible. These are constructed of metals or alloys with high thermal conductivity properties. A commonly-used metal in the design of heat sinks is copper due to its high thermal conductivity properties.
Aluminum is also effective when cost and weight are a factor. The device is mounted to the heat sink with a layer of thermal compound in between to improve the surface contact and thermal transfer between the device and the heat spreader. Fins are cut into the plates and a fan will pull the air through in a directed motion, keeping the plate—and therefore, the device—cool.
Figure 1. 13G05A Power Amplifier & Heat Sink Kit
NuWaves RF Solutions product solutions domain offers an optional heat sink specifically designed for each product that requires active heat sinking (As shown in Figure 1). These are tested with each product to monitor their ability to keep the unit cool under normal operation. They are also tested in a high-temperature environment while monitoring output power. This ensures our products will perform optimally for all of our customers’ unique applications when their own system is unable to provide adequate heat sinking. Find out more about the markets and applications that NuWaves focuses on.
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