A modified current mirror circuit for the biasing of GAAS biFET RFIC power amplifiers

摘要

This paper presents a modified current mirror topology derived from the well known two-VBE bipolar-only circuit structure used in RFIC power amplifiers. The novelty behind the proposed modified structure is that it uses a simple diode-based switching mechanism in order to maintain better bias current regulation, hence better RF gain regulation, as the reference voltage is lowered to values that are very close to the two-VBE cut-off point commonly associated with a bipolar-only voltage regulator typically found in this type of current mirror. This improved regulation is helpful in some specific GaAs BiFET power amplifier applications where the reference voltage supplied to the current mirror is guaranteed to a minimum value of ∼ 2.8 V, but requiring necessarily a bipolar-only voltage regulator structure within the current mirror in order to achieve specific dynamic biasing, control triggering or pre-distortion functions.