A 45 dB variable gain low noise MMIC amplifier

A variable gain amplifier operating at 2.5 GHz based on single ended topology has been designed and characterized. Three such stages were cascaded preceded by a single stage LNA. A source follower is used at the output as an active load matching. Overall dynamic gain variation is 45 dB with a maximum gain of 47 dB. The -3 dB bandwidth is 0.800 GHz. A minimum noise figure of 0.81 dB is obtained in the highest gain mode. Maximum value of 1 dB compression at the output is -7.2 dBm and the corresponding third order intercept point is +5.3 dBm. Consumed DC power 285 mW and is immune to gain variation. The circuit is implemented with GaAs pHEMT technology. The combined area occupied by the multistage low noise VGA and the single ended VGA is 3.5 mm /spl times/ 3 mm.