rf snubber circuit with dynamic bias

Abstract

An RF buffer circuit for a voltage controlled oscillator (VCO) includes a dynamic bias circuit to selectively invert the phase of the output voltage waveform. In a CMOS implementation, a PMOS / NMOS pair is used on the output path. During high (voltage) swing mode conditions, the phase of the output is inverted so that the output waveform is in phase with the voltage appearing at the gate of the PMOS / NMOS pair. This technique thereby reduces the peak gate-to-drain voltage and allows for improved reliability of MOS devices employing configurations that withstand low phase noise and low power consumption.

Description

technical field [0001] The present invention generally relates to RF buffer circuits used in conjunction with RF components such as voltage controlled oscillators (VCOs). Background technique [0002] Voltage controlled oscillators are well known devices used in a wide variety of RF electronics applications, such as frequency synthesizers for RF communication systems. Regardless of new developments in their design, VCOs are still considered one of the most critical design components in RF transceivers. Typically, the most important parameters of a VCO are phase noise, power consumption, and frequency tuning range. Output buffer circuits are often used to amplify the output of a VCO and isolate the VCO from load conditions. [0003] To meet the stringent phase noise specifications in 3G wireless communication standards (such as those in CDMA1X and other protocols), existing VCOs generate differential output voltages with wide swings (typically up to 3V). This wide voltage ...

AI Technical Summary

Problems solved by technology

The wide swing applied to the buffer causes it to be higher than the ideal gate-to-drain voltage V on the transistors of the buffer circuit GD and the gate-to-source voltage V GS , thereby stressing these transistors and creating reliability issues due to both hot carrier injection (HCI) and gate oxide breakdown

Reliable operation is paramount and becomes more challenging due to the use of deep sub-micron processes

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