F. van Rijs

Record power added efficiency of bipolar power transistors for low voltage wireless applications

To increase the power added efficiency (PAE) of low voltage RF bipolar power transistors for cellular applications, we investigated the influence of transistor parasitics on PAE. We found that reducing the output capacitance increases the PAE due to better second harmonic tuning. By optimizing the transistor for a low output capacitance we achieved a record PAE of 71% at 0.5 Watt, 1.8 GHz and 3.5 V supply voltage.

77% power added efficiency surface-mounted bipolar power transistors for low-voltage wireless applications

To increase the power added efficiency (PAE) and gain (G/sub p/) of low-voltage RF bipolar power transistors for cellular applications, we present a novel wafer-scale packaging concept based on our silicon-on-anything technology allowing for a strong reduction of device and packaging parasitics. Using this concept, we have achieved a record PAE of 77% and G/sub p/ of 14 dB at 0.5 W, 1.8 GHz and 3.5 V supply voltage for an assembled device approaching the theoretical class-AB limit of 78.5%. We also present a 15 V double epi-layer integrated cascode with a gain of 24 dB at 1.8 GHz.

Enhanced RF power gain by eliminating the emitter bondwire inductance in emitter plug grounded mounted bipolar transistors

For the first time, we show an enhanced RF power gain by eliminating the emitter bondwire inductance in emitter plug grounded mounted bipolar transistors. By grounding the emitter with a substrate contact to a low-ohmic substrate, the emitter bondwire is effectively short-circuited. At maximum output power, 0.5 W with a power added efficiency >60%, an increase in power gain of 2 dB, up to 14.5 dB, is observed. For 0.2 W output power, an increase of 5 dB, up to 19 dB, is observed.

RF power large signal modeling with MEXTRAM

To describe the RF performance of double polysilicon bipolar transistors, the model MEXTRAM is used for detailed modeling of the high current effects. Parameters of MEXTRAM are extracted from only small signal and DC measurements to predict the large signal behaviour. To obtain good correspondence with RF power measurements the measurement system also needed to be modeled.

High gain, high efficiency, low voltage, medium power Si-bipolar transistor suitable for integration

Medium power transistors in a high performance double polysilicon bipolar process have been fabricated. On-wafer loadpull measurements show high gain (15 dB) and high maximum efficiency (60%) at 1.8 GHz with 27 dBm of output power. These results were obtained with a low supply voltage of 3.5 V. More importantly, these results were obtained with transistors with a buried layer having a collector contact at the top, which makes it possible to integrate power amplifiers on chip.