Active-Biased Quartz Oscillator Circuit for Low-Power Stability
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Solution Overview
Problem
Existing quartz oscillator circuits face challenges in achieving low consumption while maintaining high bias impedance, which is difficult to integrate and can degrade oscillation performance, especially when produced on a silicon substrate.
Innovation Solution
The quartz oscillator circuit employs a transconductance operational amplifier as a voltage follower for active biasing between the gate and drain terminals of the transistors, along with a pseudo-resistor implemented using an NMOS transistor, to achieve high impedance without degrading the oscillation, and includes a regulation unit to adapt bias currents based on oscillation amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-value polarization resistor is used to reduce current consumption, then energy consumption is reduced, but the resistor occupies significant area on the silicon substrate and is difficult to integrate
Solution Approach 1:
The patent replaces the passive physical resistor with an active electronic circuit (operational amplifier with feedback network) that synthesizes the polarization function. This substitution allows achieving high impedance without requiring large physical resistor area on the silicon substrate, resolving the contradiction between low power consumption and integration area.
Solution Approach 2:
The patent changes the impedance characteristic dynamically through the operational amplifier circuit, which can provide high DC impedance for power saving while maintaining appropriate AC characteristics for oscillation. This parameter transformation allows the circuit to achieve high effective resistance without physical resistor area constraints.
2Use of energy by moving object
If a high-value polarization resistor is used to achieve low consumption, then current in the active branch is reduced, but the negative resistance required for maintaining oscillation may be degraded
Solution Approach 1:
The operational amplifier-based active polarization circuit replaces the passive resistor, enabling independent control of DC bias current (for power consumption) and AC negative resistance (for oscillation maintenance). The feedback network ensures that the amplifier provides the necessary negative resistance at the oscillation frequency while allowing the DC current to be minimized for low power operation.
Solution Approach 2:
The patent introduces dynamic behavior through the operational amplifier circuit, which can respond differently to DC and AC signals. The circuit dynamically adjusts the impedance characteristics based on the signal frequency, providing high DC impedance for low power consumption while maintaining the required AC negative resistance for reliable oscillation.
3Stability of the object's composition
If additional capacitors are added to stabilize the operational amplifier, then amplifier stability is improved, but the oscillator circuit size increases
Solution Approach 1:
The patent makes the existing oscillation capacitors (C1 and C2) serve dual functions: they determine the oscillation frequency and simultaneously provide the necessary feedback for amplifier stabilization. This multi-functionality eliminates the need for separate stabilization capacitors, maintaining amplifier stability without increasing circuit size.
Solution Approach 2:
The patent merges the oscillation function and amplifier stabilization function into a single circuit configuration. The feedback network uses the same capacitive elements that define the oscillation frequency, combining two functions that could have been implemented separately into one integrated solution, thus avoiding additional components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for a low-consumption quartz oscillator circuit with high bias impedance, ensuring stable oscillations without the need for additional capacitors, and is easily integrable on a silicon substrate, maintaining oscillation performance while minimizing current consumption.
Implementation Method 1
a voltage oscillation at the level of the quartz is established to produce an oscillation signal at a frequency determined by the first output electrode of the quartz
Implementation Method 2
a transconductance operational amplifier mounted as a voltage follower between the drain and gate terminals of an MOS transistor of an active branch of the oscillator circuit
Implementation Method 3
a pseudo-resistor as active biasing means... this pseudo-resistance is produced by a MOS transistor M17, the drain and source terminals of which are respectively connected to the drain and gate terminals of the MOS transistor M1
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The quartz oscillator circuit comprises an inverter formed from two complementary pMOS and nMOS transistors (P1, N1) connected in series with a current source (4) between two terminals of a supply voltage source in order to define an active branch. A source terminal of the pMOS transistor (P1) is connected to the current source, while a source terminal of the other transistor, i.e. the nMOS transistor (N1), is connected to a ground terminal. Drain terminals of the transistors are connected as output to a first electrode (XOUT) of the quartz oscillator (3), while the gate terminals of said transistors are connected as input to a second electrode (XIN) of the oscillator. A first, phase-shifting capacitor (C1) is connected to the first electrode of the oscillator, while a second capacitor (C2) is connected to the second electrode of the oscillator. The oscillator circuit includes an active-bias means (2) placed between the drain terminals and the gate terminals of the transistors of the inverter. This bias means may be a transconductance operational amplifier connected as follower and having a high enough impedance not to degrade the transconductance of the active branch for generating an oscillation in the oscillator.