A GaAs PHEMT distributed amplifier with low group delay time variation for 40 GBit/s optical systems

A four stage distributed amplifier MMIC with 11.2 dB/spl plusmn/1.0 dB gain and a bandwidth exceeding 50 GHz has been demonstrated in a commercially available 0.15 /spl mu/m pseudomorphic GaAs HEMT technology. Group delay time variation from 1.5 GHz to 40 GHz equals to /spl plusmn/3.5 ps. When used as preamplifier, biasing can be applied from a single 5.2 V supply via the reverse drain load without the need for an expensive external RF-coil for decoupling. The resulting overall power consumption is less than 230 m W. The noise figure was measured to be between 5.1dB and 3.0 dB in the band from 3 GHz to 17 GHz. The output voltage swing of the 20 GHz fundamental at the 1-dB gain compression is 2.1 V, this makes the circuit also suitable as preamplifier for a modulator driver.