A 24-dB Ku-band low-power linearized 90-nm amplifier with a built-in output buffer

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In this paper, we present a 90-nm high gain (24dB) linearized CMOS amplifier suitable for applications requiring high degree of port isolation in the Ku-band (13.2–15.4GHz). The two-stage design is composed of a low-noise common-gate stage and a gain-boosting cascode block with an integrated output buffer for measurement. Optimization of input stage and load-port buffer parameters improves the front-end's linear coverage, port return-loss, and overall gain without burdening its power demand and noise contribution. With low gate bias voltages (0.65–1.2V) and an active current source, <−10dB port reflection loss and 3.25–3.41dB NF are achieved over the bandwidth. The input reflection loss of the overall amplifier lies between −35 and −10dB and the circuit demonstrates a peak forward gain of 24dB at 14.2GHz. The output buffer improves the amplifier's forward gain by ∼9dB and pushes down the minimum output return loss to −22.5dB while raising the front-end NF by only 0.05dB. The effect of layout parasites is considered in detail in the 90-nm process models for accurate RF analysis. Monte Carlo simulation predicts 9% and 8% variation in gain and noise figures resulting from a 10% mismatch in process. The Ku-band amplifier including the buffer block consumes 7.69mA from a 1.2-V supply. The proposed circuit techniques achieve superior small signal gain, GHz-per-milliwatt, and range of linearity when compared with simulated results of reported microwave amplifiers.