Diamond Buffer Output Stage With Dynamic Current Boost
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Solution Overview
Problem
Conventional operational amplifiers face a limitation in producing substantial output current without a corresponding increase in quiescent current, which restricts their capability to meet higher output demands.
Innovation Solution
The implementation of a linear boost circuit that enhances the output current capability of a diamond buffer by sensing and mirroring increased collector currents into the base of output transistors, allowing for increased base current supply without significantly increasing quiescent current, thereby doubling the output current drive capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional diamond buffer circuitry is used, then the circuit maintains low quiescent current, but the output current drive capability is limited
Solution Approach 1:
The patent implements a preliminary boost to the bias current supplied to the diamond buffer circuitry before the output stage requires high current. A current mirror circuit pre-charges or pre-biases the input stage transistors, storing energy in the form of elevated current levels that are then available when high output current is demanded. This preliminary action allows the circuit to deliver high output current without requiring continuously high quiescent current.
Solution Approach 2:
The patent employs dynamic current mirroring where the bias current to the diamond buffer is not fixed but dynamically adjusted based on output current demands. The current mirror circuitry responds to output stage current requirements by automatically increasing or decreasing the input stage bias current, enabling the circuit to maintain low quiescent current during normal operation while rapidly boosting current delivery capability when needed.
2Power
If bias current to diamond buffer is increased to boost output current, then output drive capability improves, but quiescent current increases significantly
Solution Approach 1:
The current mirror circuit provides a preliminary current boost that is activated only when needed. Instead of continuously supplying high bias current to the diamond buffer, the mirror circuit pre-establishes the necessary current relationships and stores the boost capability, which is then deployed on-demand to enhance output drive without permanently increasing quiescent current consumption.
Solution Approach 2:
The patent changes the bias current parameter dynamically through the current mirror mechanism. The mirror ratio and activation state are adjusted based on output requirements, allowing the bias current to transition from a low quiescent level to a high drive level. This parameter change is controlled and temporary, enabling high output current capability without sustaining high quiescent current.
3Power
If conventional current mirror circuits are used, then the circuit structure is simple, but the maximum output current is limited by the bias current magnitude
Solution Approach 1:
The patent merges the current mirror function with the biasing circuitry of the diamond buffer. Instead of using separate, independent current mirror circuits, the design integrates the mirroring function directly into the bias generation path, combining multiple functions into a unified circuit structure. This merging approach increases output current capability while minimizing additional complexity by reusing existing circuit elements for multiple purposes.
Solution Approach 2:
The current mirror circuitry in the patent serves multiple functions: it provides bias current to the diamond buffer, enables output current boosting, and maintains circuit stability. By designing the mirror circuit to perform these multiple roles simultaneously, the patent achieves enhanced output current capability without proportionally increasing circuit complexity, as the same structural elements fulfill several critical functions.
Data Source
AI summary
Circuitry for increasing the maximum output current magnitude of a diamond buffer (Q57,58,74,75) having increased maximum output current provides a bias current of a first magnitude (I) into an emitter of a PNP first input transistor (Q57) and sinks a bias current of the first magnitude out of an emitter of an NPN second input transistor (Q55). The decrease is sensed in a collector current of the first input transistor caused by a demand for increased base current by a NPN first output transistor (Q74) of the diamond buffer. A collector current (Ic(65)) in an NPN another transistor (Q65) is increased in response to the decrease in the collector current of the first input transistor. The increased collector current in the first transistor is mirrored into a base of the first output transistor to boost its base current and maintain operation of the first input transistor when the amount of base current demanded by the first output transistor exceeds the first magnitude.