Bootstrap Level-Shifting Amplifier for Over-Rail Signal Linearity
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Solution Overview
Problem
Prior art level-shifting amplifiers often exhibit low input impedance and require significant bias current, which can be undesirable, especially when handling signals that exceed the supply voltage rail.
Innovation Solution
The development of level-shifting amplifier circuits with an input impedance greater than 100 MOhms, which do not require a significant bias current from the source, utilizing various configurations such as JFET-based and MOSFET-based designs to achieve high input impedance and maintain signal linearity across a wide voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional level-shifting amplifier circuits are used, then the circuit can handle input signals, but the input impedance is low and significant bias current is required
Solution Approach 1:
The patent changes the operating parameters of the amplifier by using JFET or MOSFET input stages instead of conventional bipolar transistors. This parameter change results in dramatically higher input impedance (greater than 100 MOhms) and reduced bias current requirements, directly resolving the technical contradiction between achieving high input impedance and minimizing bias current consumption.
Solution Approach 2:
The patent introduces an intermediary bootstrap capacitor connected between the output and input of the amplifier. This capacitor acts as an intermediary element that provides negative feedback to increase the effective input impedance without requiring additional bias current, thereby resolving the contradiction between high input impedance and low bias current.
2Adaptability or versatility
If the amplifier handles signals exceeding supply voltage rail, then signal range is extended, but linearity deteriorates
Solution Approach 1:
The patent employs feedback mechanisms through the bootstrap capacitor and operational amplifier configuration to maintain signal linearity even when handling input signals that exceed the supply voltage rail. The feedback loop continuously adjusts the operating point to preserve linearity across the extended voltage range, resolving the contradiction between extended signal range and maintained linearity.
Data Source
AI summary
A level-shifting amplifier is provided for level-shifting an input signal with a voltage magnitude that exceeds a supply voltage of the amplifier. In operation, the amplifier has an input impedance of greater than 100 MOhms.