Rail-to-Rail Amplifier Input Pair Switching for Lower Power
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Solution Overview
Problem
Traditional rail-to-rail amplifiers consume unnecessary power due to simultaneous operation of NMOS and PMOS input pairs across full input voltage regions, leading to increased power consumption.
Innovation Solution
Incorporation of a current transferring circuit that switches current sources between PMOS and NMOS input pairs based on input voltage levels, mimicking the current consumption of a single input pair amplifier, thereby allowing full input voltage operation with reduced power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional rail-to-rail amplifier uses both NMOS and PMOS input pairs simultaneously across full input voltage regions, then full input voltage operation is achieved, but power consumption increases due to unnecessary simultaneous operation of both input pairs
Solution Approach 1:
The patent implements dynamic switching between NMOS and PMOS input pairs based on input voltage levels. A control circuit dynamically determines which input pair should be active by comparing the input voltage with reference voltages, ensuring only one input pair operates at any given time. This dynamic adaptation maintains full input voltage range coverage while eliminating the power waste of simultaneous operation.
Solution Approach 2:
The patent introduces a current transferring circuit as an intermediary between the current source and the input pairs. This intermediary circuit selectively redirects the bias current to either the NMOS or PMOS input pair based on the input voltage level, preventing both pairs from drawing current simultaneously. The current transferring circuit acts as a mediator that enables full voltage range operation while maintaining low power consumption.
2Adaptability or versatility
If a rail-to-rail amplifier uses both NMOS and PMOS input pairs to cover full input voltage regions, then operating capability across all voltage regions is improved, but device complexity increases due to the need for additional control circuits
Solution Approach 1:
The patent merges the control functions for selecting between NMOS and PMOS input pairs into a single integrated control circuit. The control circuit combines voltage comparison, switching control, and current transfer management into one unified structure, reducing the overall complexity compared to having separate control mechanisms for each input pair. This merging approach maintains full voltage range operation while simplifying the circuit architecture.
Data Source
AI summary
An amplifier includes an output stage circuit, a current source, a PMOS input pair, an NMOS input pair and a current transferring circuit. The output stage circuit is electrically coupled to a supply voltage and a ground voltage. The current source has a node to provide a current. The PMOS input pair is coupled to the node and the ground voltage and controlled by an input voltage. The NMOS input pair coupled to the supply voltage is controlled by the input voltage. The current transferring circuit is coupled to the node and the NMOS input pair. When the input voltage is less than a specific value, the current flows into the PMOS input pair through the node. When the input voltage is larger than or equal to the specific value, the current flows into the NMOS input pair through the node and the current transferring circuit.