Amplifier RC Feedback Charging Path for Fast Turn-On Stability
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Solution Overview
Problem
Existing amplification systems face challenges in reducing turn-on time while maintaining performance under process, supply voltage, and temperature variations, with large resistance and capacitance in feedback networks prolonging turn-on times and inductor usage being limited due to cost and size constraints.
Innovation Solution
A fast turn-on amplification system incorporating a resistor-capacitor (RC) network with a charging path circuit, including a diode and CMOS or bipolar transistors, to accelerate the charging speed of the feedback capacitor, reducing turn-on time without increasing complexity or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback network with large resistance and capacitance is used to improve stability and gain flatness, then the amplification system's stability and gain flatness are enhanced, but the turn-on time is significantly increased
Solution Approach 1:
The feedback network is segmented into two distinct paths: a first feedback path containing a feedback resistor for DC feedback to maintain stability, and a second feedback path containing a feedback capacitor for AC feedback to maintain gain flatness. This segmentation allows each path to be optimized independently, resolving the contradiction between stability enhancement and turn-on time reduction.
Solution Approach 2:
A switching device is introduced as an intermediary element that selectively connects or disconnects the first and second feedback paths based on the operational state of the amplification system. During turn-on, the switching device disconnects the first feedback path to enable fast charging of the feedback capacitor, and connects it during normal operation to maintain DC stability, thus mediating between the conflicting requirements.
2Reliability
If inductors are used in the amplification system to improve performance, then the system's frequency response may be enhanced, but the cost and die size increase significantly
Solution Approach 1:
The patent replaces expensive inductors with resistors and capacitors, which are cheaper and occupy less die area. The feedback network uses readily available passive components (resistors and capacitors) arranged in a specific configuration to achieve the desired frequency response without the need for bulky inductors, thus reducing cost and die size while maintaining performance.
Solution Approach 2:
The patent changes the circuit topology from one that would require inductors to an RC-based feedback network. By adjusting the values of resistors and capacitors, the desired frequency response characteristics are achieved without using inductors, effectively changing the circuit parameters to eliminate the need for space-consuming components.
3Measurement precision
If the feedback network is designed to improve gain flatness and return loss, then the amplification system's performance characteristics are enhanced, but the turn-on time is prolonged due to large capacitance
Solution Approach 1:
The feedback network is divided into separate AC and DC feedback paths. The second feedback path with the feedback capacitor is dedicated to gain flatness and return loss optimization, while the first feedback path with the feedback resistor handles DC stability. This segmentation allows the capacitor to be sized for performance without being constrained by turn-on time requirements.
Solution Approach 2:
The switching device is configured to preemptively disconnect the first feedback path during the turn-on transient period, allowing the feedback capacitor to charge rapidly through a dedicated charging path before the DC feedback is engaged. This preliminary action ensures that gain flatness is established quickly without being limited by the RC time constant of the full feedback network.
Data Source
AI summary
The present disclosure relates to an amplification system that includes an amplifier, a resistor-capacitor (RC) network, and a charging path circuit. Herein, the RC network is coupled between an input port and an output port of the amplifier and includes a feedback resistor and a feedback capacitor. The feedback resistor is coupled between the input port of the amplifier and a joint point in between the feedback resistor and the feedback capacitor, and the feedback capacitor is coupled between the joint point and the output port of the amplifier. The charging path circuit is coupled between the joint point and ground, and configured to accelerate a charging speed of the feedback capacitor and reduce turn-on time of the amplifier.