Current Mirror Pre-Charging for Fast Power Amplifier Enable
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Solution Overview
Problem
Current mirror systems in power amplifiers face slow enable times due to large capacitances requiring a small current to charge, which hinders rapid activation.
Innovation Solution
A system and method for pre-charging current mirrors using a controller that provides both a first current and an additional current based on a reference voltage, utilizing a voltage-to-current converter to rapidly charge capacitances associated with current mirrors, with the additional current being selectively applied through control signals to minimize turn-on time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large capacitance is used in the current mirror to meet stability and noise performance requirements, then the stability and noise performance are improved, but the enable time increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitance associated with the current mirror before full activation is required. A pre-charge current path is established that charges the capacitance in advance, so when the current mirror needs to be enabled, the capacitance is already partially or fully charged, significantly reducing the enable time while maintaining the large capacitance value needed for stability and noise performance
Solution Approach 2:
The patent segments the charging process into two distinct phases: a pre-charge phase using a dedicated pre-charge current path, and a normal operation phase using the standard bias current. This segmentation allows the system to optimize for speed during enablement while maintaining stability during normal operation, resolving the contradiction between fast enable time and stable performance
2Reliability
If a relatively small current is used to charge the capacitance, then the circuit operates safely within current limits, but the charging speed becomes slow
Solution Approach 1:
The patent implements dynamic current control by using a pre-charge switch that dynamically changes the current level based on the operational state. During the pre-charge phase, a larger current is permitted to quickly charge the capacitance. Once pre-charging is complete or during normal operation, the current is limited to the safe operating level. This dynamic adjustment resolves the contradiction between safe current limits and fast charging speed
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
Significantly reduces the turn-on time of current mirrors from approximately 22 microseconds to 2.2 microseconds, enhancing the rapid activation of power amplifiers.
Implementation Method 1
a large capacitance is desired to meet stability and noise performance of the power amplifier. Unfortunately, the large capacitance gives rise to a slow enable time because a relatively small current must charge a relatively large capacitance to the bias point of the current minor before the current minor if fully activated
Data Source
AI summary
A system for pre-charging a current mirror includes a controller configured to provide a first current and an additional current to a current mirror to rapidly charge a capacitance associated with the current mirror based on a reference voltage or control signals. A power amplifier module includes at least one current minor and a controller. A capacitor is coupled to the current minor. The controller provides a bias current in an amount proportional to an input to a voltage-to-current converter. The controller receives a control signal that directs the controller to apply one of a pre-charge voltage and a nominal voltage to the voltage-to-current converter.