Integrated LDO Regulator with On-Die Equivalent Capacitance for RF Amplifier Linearity
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Solution Overview
Problem
Radio frequency amplifier circuits face challenges in maintaining linearity due to the need for high capacitance values that cannot be integrated on-die, requiring external capacitors which are impractical in miniaturized wireless communication devices, leading to pin-to-pin compatibility issues and circuit board layout constraints.
Innovation Solution
An equivalent capacitance circuit is implemented on the same semiconductor die as the radio frequency amplifier circuitry, using an operational amplifier with a capacitor and resistor configuration to define a capacitance in the nano-Farad to micro-Farad range, eliminating the need for external capacitors and maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high capacitance values (nano-Farad to micro-Farad range) are used to maintain linearity of the radio frequency amplifier, then linearity is improved, but external capacitors are required which increase device footprint and create pin-to-pin compatibility issues
Solution Approach 1:
The patent combines the LDO regulator and the required high-value capacitor into a single integrated circuit package. The regulator portion provides voltage regulation while the capacitor portion provides the necessary capacitance for amplifier linearity, eliminating the need for separate external capacitor components and their associated mounting space and pin connections.
Solution Approach 2:
The integrated circuit serves multiple functions: it acts as both a voltage regulator and a capacitor for the amplifier circuit. This multi-functional component simultaneously provides voltage regulation and the high capacitance needed for maintaining amplifier linearity, reducing the overall component count and device footprint.
2Manufacturing precision
If external capacitors are used to maintain amplifier linearity, then linearity is improved, but pin-to-pin compatibility issues and circuit board layout constraints arise
Solution Approach 1:
The regulator and capacitor are merged into one component, eliminating the need for separate capacitor mounting and connection to the circuit board. This integration removes the layout constraints and pin-to-pin compatibility issues that would otherwise arise from connecting external capacitors.
3Power
If the dropout voltage of the regulator is increased to accommodate higher current consumption, then power delivery capability is improved, but linearity is degraded
Solution Approach 1:
The integrated high-value capacitor acts as an intermediary energy storage element that decouples the power delivery requirements from the linearity requirements. It provides the necessary charge reservoir to maintain low equivalent series resistance and good linearity even when the regulator operates at higher dropout voltages for high current applications.
Solution Approach 2:
The patent changes the capacitance parameter to very high values (nano-Farad to micro-Farad range) which fundamentally alters the electrical characteristics of the circuit. This high capacitance compensates for the increased dropout voltage by providing sufficient charge storage to maintain low equivalent series resistance, thereby preserving linearity despite the higher dropout voltage necessary for high current operation.
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 solution allows for integrated low dropout voltage regulators within radio frequency amplifier circuits, maintaining high linearity without external capacitors, thus addressing the impracticality of external capacitor implementation in miniaturized devices.
Implementation Method 1
An equivalent capacitance circuit is implemented on the same semiconductor die as the radio frequency amplifier circuitry, using an operational amplifier with a capacitor and resistor configuration to define a capacitance in the nano-Farad to micro-Farad range
Data Source
AI summary
A radio frequency amplifier circuit has a signal input and a signal output. A primary amplifier is connected to the signal input and the signal output. A low dropout voltage regulator is connectible to an external power supply and to the primary amplifier, and generates a set voltage to bias the primary amplifier from a variable voltage provided by the external power supply. An equivalent capacitance circuit is connected to the primary amplifier and to the low dropout voltage regulator. The equivalent capacitance circuit defines a low dropout voltage regulator output capacitance in a nano-Farad to micro-Farad range absent any passive capacitor components corresponding thereto to maintain linearity of the primary amplifier.