At least one example embodiment provides a controller to sample a first signal. The first signal indicates an initial amplitude of an output signal of an oscillator circuit. The controller selects a step amount based on the first signal and a target amplitude of the output signal. The controller generates a control signal for the oscillator circuit based on the selected step amount. The control signal indicates a change in gain for the oscillator circuit according to the selected step amount.

An oscillation circuit includes a circuit for oscillation that oscillates a resonator, an output circuit that has a signal, output from the circuit for oscillation, input thereto to thereby output an oscillation signal, a connection terminal to which power is applied, a first wiring that connects from the connection terminal to the output circuit, and a second wiring that is connected to the first wiring through a connection node provided on the first wiring and connects from the connection node to the circuit for oscillation. The circuit for oscillation, the output circuit, the connection terminal, the first wiring, and the second wiring are provided on a semiconductor substrate. The length of a wiring extending from the connection terminal of the first wiring to the connection node is shorter than the length of the second wiring.

An oscillation circuit includes a circuit for oscillation and a signal adjustment circuit connected to the circuit for oscillation. An input voltage based on a direct-current voltage, a voltage value of which can be changed, is input to the circuit for oscillation and the signal adjustment circuit. The circuit for oscillation causes a vibration piece to oscillate and outputs a first oscillation signal. A frequency of the first oscillation signal is adjusted according to the voltage value output from the signal adjustment circuit.

An oscillation circuit includes a circuit for oscillation that oscillates a resonator, an output circuit that has a signal, output from the circuit for oscillation, input thereto to thereby output an oscillation signal, a connection terminal to which power is applied, a first wiring that connects from the connection terminal to the output circuit, and a second wiring that is connected to the first wiring through a connection node provided on the first wiring and connects from the connection node to the circuit for oscillation. The circuit for oscillation, the output circuit, the connection terminal, the first wiring, and the second wiring are provided on a semiconductor substrate. The length of a wiring extending from the connection terminal of the first wiring to the connection node is shorter than the length of the second wiring.

An electronic device comprises an oscillator circuit portion comprising an inverter and a crystal oscillator connected between the input and output terminals of the inverter. An amplitude regulator circuit portion is arranged to supply a current to the inverter. The amplitude regulator monitors a voltage at the input of the inverter and varies the current supplied to the inverter in response to the monitored voltage. The amplitude regulator comprises a trimmable resistor arranged such that the voltage at the input of the inverter is set to an operating point when the supply current is equal to a threshold value, the operating point being at least partly determined by the selected resistance of the resistor. A current monitor is arranged to monitor the current supplied to the inverter during operation and to determine therefrom whether the voltage at the input terminal of the inverter is within a predetermined range.

Provided is a method for controlling the bias current, I.sub.PIERCE, of an oscillator. The method includes acquiring or determining a digital representation encoding a bias current. The method also includes carrying out an algorithm to update the digital representation if the oscillation amplitude is measured, by one or more peak detectors, to be outside of upper and lower thresholds. Also provided is an apparatus arranged to control the bias current of an oscillator using this method, the apparatus including one or more peak detectors and a current digital to analogue converter.

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.