Active Load Generation Circuit for Impedance Stability

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Solution Overview

Problem

Modern integrated circuits face challenges in reducing the area occupied by passive components, such as resistors and capacitors, while maintaining impedance stability against process, voltage, and temperature variations.

Innovation Solution

An active load generation circuit using a transistor, voltage control circuit, temperature sensing circuit, and voltage offset and tracking circuit is implemented, which generates a control voltage to adjust impedance based on input signals and ambient temperature, reducing susceptibility to process, voltage, and temperature variations and saving circuit area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If passive components (resistors and capacitors) are used to generate impedance in integrated circuits, then the impedance is stable against process, voltage, and temperature variations, but the circuit area occupied by these passive components becomes large

Engineering Contradiction:

Improveimpedance stabilityVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent uses a transistor whose impedance parameter is dynamically controlled by a control voltage. By changing the control voltage, the impedance of the transistor can be adjusted to match the desired impedance value, replacing the need for large passive components while maintaining the required electrical characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces passive mechanical/electrical components (resistors and capacitors) with an active transistor-based system. The transistor, controlled by voltage signals, substitutes for the passive impedance-generating components, enabling area reduction while maintaining functional equivalence

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Area of stationary object

If active components are used to replace passive components to save area, then the circuit area is reduced, but the impedances of active components become more susceptible to process, voltage, and temperature variations

Engineering Contradiction:

Improvecircuit areaVSAvoidimpedance stability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent introduces a feedback mechanism where the control voltage is adjusted based on the actual impedance requirements. The voltage control circuit monitors and adjusts the control voltage applied to the transistor, ensuring that the impedance remains stable despite variations in process, voltage, and temperature conditions

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent makes the transistor impedance dynamic and controllable through voltage adjustment. Instead of using fixed passive components, the system dynamically adjusts the transistor's operating point via control voltage to maintain stable impedance characteristics under varying environmental conditions

Inventive Principle:

Principle #15Dynamics

3Length of moving object

If a large on-chip capacitor is manufactured to achieve low cutoff frequency, then the resistor can be made small, but the manufacturing complexity and area increase

Engineering Contradiction:

Improveresistor sizeVSAvoidmanufacturing difficulty

Core Design Contradiction:

Length of moving objectVSEase of manufacture

Solution Approach 1:

The patent changes the approach from using large capacitor values to achieve low cutoff frequency to using a voltage-controlled transistor impedance. By adjusting the control voltage, the effective resistance is changed, allowing low cutoff frequencies to be achieved without requiring large physical capacitor or resistor dimensions

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10461734B2Active load generation circuit and filter using same

Publication Date: 2019.10.29 REALTEK SEMICON CORP

AI summary

This invention discloses an active load generation circuit and a filter. The active load generation circuit includes a transistor, a voltage control circuit, a voltage offset and tracking circuit, and a temperature sensing circuit. The transistor provides an impedance and includes a control terminal and an input terminal. The control terminal receives a control voltage, the input terminal receives an input signal, and the impedance is associated with the control voltage. The voltage control circuit generates an intermediate voltage according to a power supply voltage and a first reference voltage. The voltage offset and tracking circuit generates the control voltage according to the input signal and the intermediate voltage such that the control voltage varies with the input signal. The temperature sensing circuit senses an ambient temperature of the active load generation circuit and adjusts the first reference voltage according to the ambient temperature.