A 45-dB variable-gain low-noise MMIC amplifier

A variable-gain amplifier (VGA) operating at 2.5 GHz based on single-ended topology has been designed and characterized. Three such stages were cascaded and preceded by a single-stage low-noise amplifier. A source follower was used at the output in order to achieve excellent output match. The variation gain is 45 dB with a maximum gain of 47 dB. The -3-dB bandwidth is 0.8 GHz. Minimum noise figure of 0.81 dB is obtained in the highest gain mode. The highest output power, corresponding to 1-dB compression point is -7.2 dBm and the corresponding output third-order intercept point is +2 dBm. The circuit is implemented in a GaAs 0.15-mum pseudomorphic high electron-mobility transistor technology. The combined area occupied by the multistage low-noise VGA and the single-ended VGA is 3.5 mm times 3 mm