The voltage-dependent IP3 performance of a 35-GHz InAlAs/InGaAs-InP HBT amplifier

Here we report on the first IP3 results of a 35-GHz Ka-band amplifier based on InAlAs/InGaAs-InP heterofunction bipolar transistors (HBT's). The amplifier combines four 1×10 μm
²
quad-emitter HBT devices for a total emitter area of 160 μm
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to achieve a gain of 5 dB and an IP3 of 26.5 dBm at 35 GHz. IP3 was characterized over collector bias voltage and indicates that there is an optimum V/sub ce/, corresponding to a maximum IP3 to DC power ratio, which is related to the HBT nonlinear voltage-dependent collector-base capacitance. A maximum IP3-to-DC power linearity figure of merit (LFOM) of 4.1 is achieved at a total collector current of 48 mA and a low V/sub ce/ of 2.25 V, This LFOM is comparable to HEMT's at these frequencies and is expected to improve with the maturity of InAlAs/InGaAs-InP HBT technology.