A Digitally Programmable Wide Tuning-Range Active Transformer for Inductorless BPF and DCOs

In this brief, a programmable active transformer based on cascode grounded active inductor is proposed. The coarse tuning is achieved by programming the digitally controlled current mirrors (DCCMs), while the fine tuning is obtained by an analog voltage applied to the varactors. A wide tuning range, high-Q LC-oscillator and an active band-pass filter (BPF) are demonstrated using the proposed active transformer. The circuits are designed and simulated in a 0.13 μm standard CMOS technology. An inductance tuning range from 7.91 nH to 4.4 μH is achieved for the active transformer. A frequency range from 0.25 GHz to 5.3 GHz and a quality factor of 24697 are obtained at the frequency of 2.46 GHz. Using 6-bit digital code, the output frequency of inductorless oscillator is programmed from 215 MHz to 2.85 GHz. For the BPF, a central frequency from 170 MHz to 2.9 GHz is obtained. A power from 21.96 mW to 28.15 mW using a supply voltage of 1 V is consumed. The proposed active transformer occupies an area of 0.004 mm². A prototype of inductorless oscillator is implemented by CD4007UBE ICs to verify the concept.