Self-Biased Quartz Oscillator With Integrated Amplitude Regulation
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Solution Overview
Problem
Existing quartz oscillator circuits face challenges in integrating high-value polarization resistance without occupying significant space, inefficiencies in bias current usage, and require external polarization sources, which hinder miniaturization and power efficiency.
Innovation Solution
A self-polarized quartz oscillator circuit that integrates amplitude regulation and polarization functions within a single electronic unit, using a bias transistor and current mirrors to modulate the bias current and reduce component count, enabling self-biasing and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a large bias resistor is used to reduce current in the active branch, then power consumption is reduced, but the resistor occupies significant space in the integrated circuit
Solution Approach 1:
The patent combines the biasing function with the amplitude regulation function into a single electronic unit. The bias transistor's gate is connected to the amplitude regulation circuit, allowing the same transistor to perform both polarization and amplitude control, thereby eliminating the need for a separate large-area resistor while maintaining low power consumption.
Solution Approach 2:
The bias transistor is designed to serve multiple functions: it provides the necessary polarization for the quartz crystal and simultaneously responds to amplitude regulation signals. This multi-functional design allows the circuit to achieve both current reduction and compact layout without requiring separate dedicated components for each function.
2Reliability
If external current sources are used for biasing, then the oscillator can operate, but the circuit requires external polarization sources which hinders miniaturization
Solution Approach 1:
The oscillator circuit is designed to be self-biasing, where the bias transistor automatically establishes the necessary operating conditions for the quartz crystal without requiring external polarization sources. The transistor's inherent characteristics and its connection to the amplitude regulation circuit enable it to self-regulate the bias current, eliminating external components and facilitating miniaturization.
3Ease of manufacture
If bias current is supplied through diode-connected transistors, then the circuit can be implemented, but the bias current is lost and does not contribute to the active branch operation
Solution Approach 1:
The patent extracts the bias current path from the diode-connected transistor configuration and redirects it through the bias transistor's source terminal directly to the active branch. This extraction eliminates the current loss that occurred in the diode connection, as the bias current now flows usefully through the NMOS transistor in the active branch, contributing to the oscillation rather than being dissipated.
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
The self-biased quartz oscillator circuit (1) comprises an amplifier (Mgmn, Mgmp) with an output connected to a first quartz electrode (Xtal) and an input connected to a second quartz electrode, an output capacitor (Cout) connected to the first quartz electrode and an input capacitor (Cin) connected to the second quartz electrode. The amplifier is biased by a current through an MOS bias transistor (MB1) generated in an amplitude regulation assembly, which further comprises an amplitude regulation stage. The second electrode of the quartz is connected to the gate of the bias transistor and to the amplitude regulation stage to modulate the bias current and regulate the amplitude of oscillation of the quartz.