What is special about LDMOS transistors?

 Heard one friend mentioning on 40m that his new linear power supply has provision for 50 Volts needed for LDMOS. Saw a mention of LDMOS on the QRZ page of another ham as well. That prompted a readup on LDMOS as I was not familiar with it. LDMOS stands for Laterally Diffused Metal Oxide Semiconductor and is a type of MOSFET or Metal Oxide Semiconductor Field Effect Transistor. They are designed for high power and high frequency applications. That would explain why it is being used in amateur radio linear amplifiers. Lateral diffusion of the source and drain region enhances the transistor’s ability to handle higher voltages and power effectively. They have high power density, linearity, efficiency, high breakdown voltage and low on-resistance. On-resistance of a MOSFET, also known as the drain-source on-resistance, is the resistance between the drain and source of the MOSFET when it's in the on state.

As already mentioned, they are useful in construction amateur radio linear amplifiers. Commercial uses would be for Radars and Cellular Network Base Stations. The three terminals of an LDMOS are source, gate and drain. In typical configurations, voltage on the gate controls the flow of current from the drain to the source. Most common configuration used is the common source configuration, in which source is grounded and drain connected to the DC supply voltage. Gate is used to induce a field-enhanced depletion region between the source and the drain. Dopant for creating P-type semiconductor region is Boron and for the N-type semiconductor region it is Arsenic. LDMOS transistors can operate from 1 MHz to 4 GHz, quite sufficient for most of the amateur radio applications. GaN (Gallium Nitride) transistors can be considered for applications beyond that range, though currently not used for usual amateur radio operations in my region. QO 100 downlink frequency is on 10 GHz band, but the receivers do not need high power RF transistors.