Power amplifier protection by adaptive output power control

A. Bezooijen, van, F.E. van Straten, R. Mahmoudi, A.H.M. Roermund, van

Research output: Contribution to journalArticleAcademicpeer-review

12 Citations (Scopus)


Abstract Cellular phone power amplifiers (PAs) operate in strongly varying environments and have to withstand extreme conditions. To avoid destructive breakdown a generic protection concept is proposed that is based on adaptive control of the output power. It provides over-voltage, over-temperature, and/or over-current protection by detection of the collector peak voltage, die temperature, and/or collector current to reduce the effective power control voltage once a threshold level is crossed. By applying protections, PAs can be implemented in low-cost silicon technology competitively to GaAs HBT implementations. In addition, requirements on package thermal resistance are relaxed. In this paper a theoretical analysis is given on the behavior of a class-AB amplifier under mismatch conditions. Measurement results on a silicon bipolar power transistor with integrated protection circuits are presented, proving the concept of adaptive protection. For a supply voltage of 5 V and nominal output power of 2 W no breakdown is observed for a VSWR of 10 over all phases when output power is adaptively reduced by 2.7 dB at most.
Original languageEnglish
Pages (from-to)1834-1841
Number of pages8
JournalIEEE Journal of Solid-State Circuits
Issue number9
Publication statusPublished - 2007


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