A low voltage crystal oscillator (XTAL) driver with feedback controlled duty cycling for ultra low power biases an amplifier for an XTAL in the sub-threshold operating regime. A feedback control scheme can be used to bias the amplifier for an XTAL biased in the sub-threshold operating regime. The amplifier of a XTAL oscillator can be duty cycled to save power, e.g., the XTAL driver can be turned off to save power when the amplitude of the XTAL oscillation reaches a maximum value in range; but be turned back on when the amplitude of the XTAL oscillation starts to decay, to maintain the oscillation before it stops. In addition or alternatively, a feedback control scheme to duty cycle the amplifier of a XTAL oscillator can be used to monitor the amplitude of the oscillation.

A low voltage crystal oscillator (XTAL) driver with feedback controlled duty cycling for ultra low power biases an amplifier for an XTAL in the sub-threshold operating regime. A feedback control scheme can be used to bias the amplifier for an XTAL biased in the sub-threshold operating regime. The amplifier of a XTAL oscillator can be duty cycled to save power, e.g., the XTAL driver can be turned off to save power when the amplitude of the XTAL oscillation reaches a maximum value in range; but be turned back on when the amplitude of the XTAL oscillation starts to decay, to maintain the oscillation before it stops. In addition or alternatively, a feedback control scheme to duty cycle the amplifier of a XTAL oscillator can be used to monitor the amplitude of the oscillation.

An oscillator and method for generating a signal are provided. The oscillator comprises an electro-mechanical resonator and a reconfigurable oscillator driver. The reconfigurable oscillator driver starts the oscillator in single-ended mode to avoid latching and transitions the oscillator to differential mode in such a manner as to sustain oscillations therein. The reconfigurable oscillator driver may comprise two back-to-back banks of inverters and an adjustable feedback resistor. In single-ended mode, one bank is disabled and the other bank is enabled. To transition to differential mode and improve the quality of the signal, the number of enabled inverters is equalized in both banks.

A low voltage crystal oscillator (XTAL) driver with feedback controlled duty cycling for ultra low power biases an amplifier for an XTAL in the sub-threshold operating regime. A feedback control scheme can be used to bias the amplifier for an XTAL biased in the sub-threshold operating regime. The amplifier of a XTAL oscillator can be duty cycled to save power, e.g., the XTAL driver can be turned off to save power when the amplitude of the XTAL oscillation reaches a maximum value in range; but be turned back on when the amplitude of the XTAL oscillation starts to decay, to maintain the oscillation before it stops. In addition or alternatively, a feedback control scheme to duty cycle the amplifier of a XTAL oscillator can be used to monitor the amplitude of the oscillation.

A transceiver comprising a tank circuit, a variable differential conductance, VDC, coupled to the tank circuit, and a variable resistance coupled to the VDC is disclosed. The variable resistance is arranged to bias the VDC into a region of positive differential conductance during a first state of operation of the transceiver, and bias the VDC into a region of negative differential conductance during a second state of operation of the transceiver.

An oscillator and method for generating a signal are provided. The oscillator comprises an electro-mechanical resonator and a reconfigurable oscillator driver. The reconfigurable oscillator driver starts the oscillator in single-ended mode to avoid latching and transitions the oscillator to differential mode in such a manner as to sustain oscillations therein. The reconfigurable oscillator driver may comprise two back-to-back banks of inverters and an adjustable feedback resistor. In single-ended mode, one bank is disabled and the other bank is enabled. To transition to differential mode and improve the quality of the signal, the number of enabled inverters is equalized in both banks.

A low voltage crystal oscillator (XTAL) driver with feedback controlled duty cycling for ultra low power biases an amplifier for an XTAL in the sub-threshold operating regime. A feedback control scheme can be used to bias the amplifier for an XTAL biased in the sub-threshold operating regime. The amplifier of a XTAL oscillator can be duty cycled to save power, e.g., the XTAL driver can be turned off to save power when the amplitude of the XTAL oscillation reaches a maximum value in range; but be turned back on when the amplitude of the XTAL oscillation starts to decay, to maintain the oscillation before it stops. In addition or alternatively, a feedback control scheme to duty cycle the amplifier of a XTAL oscillator can be used to monitor the amplitude of the oscillation.

A circuit device is configured to switching between a first mode in which phase noise of an output clock signal is lower than that in a second mode and the second mode in which power consumption is smaller than that in the first mode, and the circuit device includes an oscillation circuit configured to generate an oscillation signal, a waveform shaping circuit configured to perform waveform shaping on the oscillation signal to obtain a rectangular wave clock signal; and an output circuit configured to output the output clock signal based on the clock signal. A driving capability of the waveform shaping circuit in the first mode is higher than a driving capability of the waveform shaping circuit in the second mode.

A BIST system and method for a crystal oscillator amplifier including current mirror circuitry, an ADC, a DAC, and test control circuitry. The amplifier includes a current source, a base transistor and a feedback resistor. The ADC converts a self-bias voltage on an input node into a digital bias code during a normal mode when the current source is coupled to the base transistor. During phases of a test mode, the base transistor is coupled instead to the mirror circuitry, which mirrors current through the base transistor into a test resistor. The digital bias code is converted into upper and lower digital bias codes using a delta value, which are converted by the DAC into corresponding bias voltages driven onto the input node during respective phases of the test mode. The ADC converts corresponding test voltages on the test resistor into test codes used to estimate the amplifier transconductance.