Active Inductor Circuit for Stable Frequency and Dynamic Range
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Solution Overview
Problem
Conventional active inductors in amplifier circuits suffer from reduced dynamic range due to direct electric current voltage drops and unstable frequency characteristics, which are influenced by the load's frequency characteristics.
Innovation Solution
An active inductor configuration using a PMOS transistor with a diode-connected NMOS transistor and a capacitor between the gate and power source, along with an electric current source providing a bias current, which allows for a small-signal impedance representation and adjustable transfer conductances to stabilize impedance and frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive element such as a resistor or capacitor is combined with an active element to create an active inductor, then the amplifier circuit can achieve inductive load characteristics, but a direct electric current voltage drop occurs at the load which reduces the dynamic range of the amplifier circuit
Solution Approach 1:
The patent introduces an operational amplifier as an intermediary active element that mediates between the inductive load requirement and the voltage drop problem. The op-amp configured as a voltage follower buffers the voltage signal, preventing direct current voltage drops at the load while maintaining inductive characteristics through feedback control.
Solution Approach 2:
The patent replaces the traditional passive RC circuit mechanism with an active electronic system using operational amplifiers. This substitution eliminates the need for large voltage drops required by passive elements, allowing the circuit to achieve inductive behavior through active voltage control rather than passive component characteristics.
2Adaptability or versatility
If an active inductor is used as a load in an amplifier circuit, then the frequency characteristic of the amplifier circuit is influenced by the frequency characteristic of the load, but the dynamic range is reduced due to voltage drop
Solution Approach 1:
The patent employs feedback mechanisms through operational amplifiers to maintain stable frequency characteristics independent of load variations. The feedback loop continuously adjusts the voltage signal to compensate for load effects, preserving both the desired frequency response and the dynamic range by preventing excessive voltage drops.
3Use of energy by moving object
If bias current is increased to reduce voltage drop at the load, then the dynamic range improves, but the power consumption increases
Solution Approach 1:
The patent replaces the passive current-based voltage drop compensation mechanism with an active voltage control system using operational amplifiers. This allows the circuit to achieve the desired dynamic range through voltage amplification rather than increasing bias current, thereby maintaining performance while reducing power consumption.
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 achieves a large electric voltage drop with minimal bias current, reducing power consumption and maintaining stable impedance and frequency characteristics across varying power source voltages and temperatures.
Implementation Method 1
a capacitor (13) between a gate of the PMOS transistor (11) and the power source supply line (10)
Implementation Method 2
a diode element (12) that is connected between a drain and a gate of the PMOS transistor (11)
Data Source
AI summary
According to an embodiment, an active inductor has a first conductivity type MOS transistor with a source that is connected to an electrical power source supply line and a drain that is connected to an output terminal. It has a capacitance between a gate of the first conductivity type MOS transistor and the electrical power source supply line. It has a diode element that is connected between a drain and a gate of the first conductivity type transistor. It has an electric current source that supplies a bias electric current in a forward direction to the diode element.