A MIM-cap free digitally tunable NMOS Pi-network

A Pi-network topology using MIM-cap free digitally NMOS capacitors is demonstrated. Based on a 130 nm Bulk-CMOS process of Infineon Technologies, this circuit contains stacked transistors to vary the capacitance. It also features a direct through mode between ports to draw the minimum insertion losses of 0.36 dB at 824 MHz. The 3 capacitances can be modified from 0.2 pF to 3 pF and show a Maximum Q-factor of 90 at 900 MHz. Some additional parallel switches are added at either Input and Output to add external inductors making the circuit even more flexible. The size of the chip, including the charge pump, voltage regulator and digital MIPI control interface, is only 1600×1400 μm
²
. The circuit draws a current of 110 μA at 3.5 V operation.