Class-D CMOS Oscillators

A 1/f Noise Upconversion Reduction Technique for Voltage-Biased RF CMOS Oscillators

“…11(d) and 14(d), respectively, are designed in 40 nm CMOS to demonstrate the suppression of the 1/f noise upconversion. For fair comparison, we attempted to design the oscillators with the same specifications, such as center frequency, tuning range, and supply voltage, as their original reference designs in [4] and [5]. …”

“…11(b)], and it exhibits a strong 1/f noise upconversion and frequency pushing. A version of class-D with a tail filter technique [30] was also designed in [4] in an attempt to reduce the low-frequency noise upconversion. This method is partially effective, lowering the 1/f 3 PN corner from 2 to 0.6-1 MHz.…”

25.4 A 1/f noise upconversion reduction technique applied to Class-D and Class-F oscillators

“…To demonstrate how this technique can reduce the flicker noise up-conversion, we employ the F2-tank to a class-D [5], and F2,3-tank to a class-F [4] oscillator. These classes of oscillator are chosen for their strong amount of IH2.…”

“…The original class-D oscillator shows promising performance in the 1/f 2 region but it suffers from the strong 1/f noise up-conversion and frequency supply pushing. All known mitigation techniques (e.g., [6] [6] was also designed in [5]. A resonator at 2ω0 is interposed between the common source of the transistors and ground.…”

Analysis of power consumption in LC oscillators based on the inversion coefficient

“…Indeed, the bias transistor has been removed forcing the oscillator to work in the "voltage controlled" regime instead of the "current controlled". The oscillation amplitude is set by V DD and it is allowed to peak well above boosting the voltage efficiency (A diff /V DD ), while the current consumption depends either on V DD or on the tank losses [7]. Moreover, the differential transistors don't work anymore as transconductors but as switches: when active they are in triode region, since their gate voltage is close to V DD and the drain voltage falls to ground.…”