A four stage distributed amplifier MMIC with 11.2 dB 1.0 dB gain and a bandwidth exceeding 50 GHz has been demonstrated in a commercially available 0.15 µm pseudomorphic GaAs HEMT technology. Group delay time variation from 1.5 GHz to 40 GHz equals to 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 mW. The noise figure was measured to be between 5.1 dB 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.

In this paper, we report on two Distributed Amplifier (DA) concepts for 40 Gb/s modulator drivers. Both amplifiers are fabricated in a commercially available 150 nm GaAs power pHEMT technology. The first DA is a six stages design with capacitive division on the gate line. Gain and bandwidth of this amplifier equal to 13.2 dB and 41 GHz, respectively. The other DA consists of nine cascode stages, achieving 20.1 dB gain and a bandwidth of 34.5 GHz. Output power of the two amplifiers is higher than 21 dBm or 7 V pp up to 20 GHz, which makes them suitable for driving lithium-niobate (LiNbO 3 ) modulators.