Considering When GaN is Used Instead of LDMOS

GaN is considered to be the modern technology and material foundation when it comes to developing power amplifiers. In turn, LDMOS is the mass-market technology that has served in many commercial applications in the form of transistor amplifiers. But with which motivation is there now a change in a new design?

• Gallium nitride as a III-V semiconductor has some physical properties that become evident in the design of a transistor. Some points are worth mentioning:
• The power density is higher with GaN compared to LDMOS, which    physically   leads to  a mechanically smaller transistor chip, with higher output power.
• The efficiency is higher, which means  less loss of power, thus less cooling costs. Thus, smaller heat sinks withs maller fans are used, which in turn saves costs as well.
• GaN is a material with a large electronic band gap, which in the case of  transistors leads to the fact that large drain voltages can be applied.
• GaN- based transistors react more robust against short and open circuit. Depending on the design, this eliminates costly circulators / insulators.

A gallium nitride (GaN) high electron mobility transistor (HEMT)

• GaN  High Mobility Electron Transistors have smaller parasitic capacitances compared to LDMOS FETs of  comparable output power. The transistors have more gain with large input and output impedance. The matching circuit requires fewer stages and thus offers higher bandwidth.

All in all, there are many reasons for using GaN transistors. The technology is also establishing itself mostly  in the lighting market in the form of LEDs. The raw material throughput is thus given. Prices are falling, and in the RF transistor sector, commercialization is catching on, not least due to the increased use of plastic housings. In the meantime, transistors based on GaN are already being used in the mobile phone base station business. Other target markets such as 5GHz WIMAX applications are already addressed today.