Dynamic Bias Control Circuit for Low Voltage Amplifiers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS operational amplifiers require a supply voltage greater than the minimum needed to bias stacked diode-connected transistor branches, limiting their ability to operate at lower supply voltages, which is a challenge in designing electronic systems that require low voltage supply operations.
Innovation Solution
A dynamic bias control circuit is introduced, utilizing a configuration with PMOS and NMOS transistors and capacitors to provide a bias voltage equal to (Vaa−2Vgsp) and (2Vgsn) to the gates of transistors M3 and M4, respectively, allowing for reduced supply voltage operation by selectively coupling storage elements to reference voltages and current sources during charge and output phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If stacked diode-connected transistor branches are used to bias the amplifier, then the amplifier can operate with sufficient bias current, but the supply voltage must be greater than 2Vgs which increases the minimum supply voltage requirement
Solution Approach 1:
The patent employs dynamic bias control where the bias voltage is adjusted based on operational phase (charge vs. output). During charge phase, a higher bias voltage is applied to ensure sufficient charging current, while during output phase, the bias voltage is reduced to minimize power consumption. This dynamic adjustment resolves the contradiction by adapting the supply voltage requirement to the actual operational needs of the amplifier stages.
Solution Approach 2:
The invention changes the bias voltage parameter dynamically based on the operational phase of the amplifier. By switching between different bias voltage levels (higher during charge, lower during output), the system maintains sufficient bias current when needed while reducing the minimum supply voltage requirement during other phases, thereby resolving the contradiction between adequate biasing and low voltage operation.
2Reliability
If conventional bias circuitry is used, then the amplifier maintains stable operation, but it cannot operate at lower supply voltages which limits portability and power efficiency
Solution Approach 1:
The patent introduces dynamic bias control that adjusts operating parameters based on the amplifier's operational phase. During charge phase, the circuit operates with higher bias currents to ensure stable charging operation, while during output phase, it transitions to lower bias currents. This dynamic adaptation maintains reliability during critical operations while enabling lower supply voltage operation during other phases, thus resolving the contradiction between stable operation and low voltage capability.
Solution Approach 2:
The invention implements periodic switching between charge phase and output phase with corresponding bias adjustments. The bias circuitry periodically changes its operating point to match the operational requirements, ensuring stable operation during charge phases while enabling low-voltage operation during output phases. This periodic action resolves the contradiction by alternating between high-reliability mode and low-power mode.
Data Source
AI summary
Embodiments of the invention comprise methods, apparatuses and systems for a dynamic bias control circuit configured to dynamically bias an amplifier. The dynamic bias control circuitry includes four branches. Each of the four branches includes a transistor operably coupled in series between a current source and a reference voltage. Each branch also includes a storage element having a first terminal and a second terminal and configured for selectively coupling the first terminal to the reference voltage, selectively coupling the first terminal to a node located between the current source and a drain of the transistor, selectively coupling the second terminal to the node, and selectively coupling the second terminal to an output.