The Indestructible LDMOS

NXP BLF188 and BLF184

Mailbag today 2 ! This time from NXP. OMFG, look what I got ! This baby will definitely end up in a power RF amplifier for my Ham Radio fun time. This will be a project. THANK YOU NXP !

Got them both today ! And I have to tell you, the girls and guys at NXP really rock !!!

Some time ago I got a newsletter announcement from NXP introducing this new XR (eXtra Rugged) series of LDMOS. LDMOS stands for lateral double-diffused MOSFET, the lateral version of power MOSFET, DMOS.

There are two major structural categories of RF MOSFETs in use today. These structures, DMOS (double-diffused Metal-Oxide-Semiconductor) and LDMOS (laterally diffused Metal-Oxide-Semiconductor), have unique behaviors: semiconductor process and geometry dependent.

Both of these MOSFETs are composed of three terminal devices (assuming substrate shorted to source), commonly identified as the source, gate and drain, where the voltage on the gate controls the current flowing from the drain to the source. The most common circuit configuration for these devices is the common source (CS) configuration, which is comparable (in some respects) to the common emitter configuration of the bipolar transistor. Considering this, any frequency-dependent source to ground connection will introduce negative feedback. Other configurations are used but under the CS configuration the drain is connected to the high DC voltage while the source is grounded. The gate is used to induce a field-enhanced depletion region between the source and drain, and thereby creating a “channel”.

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