Design of an integrated cascode cell for compact Ku-band power amplifiers

This paper reports on the design of a new power cell dedicated to Ku-band power amplifier (PA) applications. This cell called “`integrated cascode'” has been designed in order to propose a strong decrease in term of circuit size for Power Amplifier (PA). The technology used relies on 0.25-μm GaAs Pseudomorphic High Electron Mobility Transistors (PHEMT) of United Monolithic Semiconductors (UMS) foundry. A distributed approach is proposed in order to model this power cell. The challenge consists to obtain, with a better shape factor (ratio between the vertical and horizontal sizes of the transistor), the same performances than a single transistor with the same gate development. In order to design a 2W amplifier, we have used two 12×100 μm transistors. Cascode vertical size is 413 μm whereas a transistor with the same gate development exhibits a vertical size of 790 μm. Therefore the shape factor is nearly one as compared to a shape factor of 4 for a classical parallel architecture. This new device allows to decrease the MMIC amplifier area of 40 % compared with amplifier based on single transistors.