Active tunable nanoscale CMOS BALUN based on operational transconductance amplifier

In modern communication systems, the signal splitter and combiner called BALUN (BALance to UNbalance) is required to interface a single ended device with a differential ended device. Most active BALUN deploy passive elements which cannot be tuned and requires large area in the integrated circuit. Though there is the controllable BALUN based on BiCMOS CCCII, the implementing circuit is quite large in transistor count and the cost of BiCMOS is very expensive. In this work, the new active BALUN based on CMOS OTA is proposed. By adjusting the transconductance of the composed OTAs, the characteristics of BALUN can be tuned electronically. Normally the size of the OTA is half of the size of the CCCII in transistor count. Therefore, the size of proposed structure is theoretically half of the CCCII counterpart. The design structure is simulated in the HSPICE based on the 90nm IBM RF-CMOS process parameters extracted by MOSIS. The result shows that the proposed structure can be a fair alternative in BALUN design via adequate compatibility of BALUN characteristics such as power-splitting, power-combination and phase inverting.