Chopper-Stabilized Amplifier Input Isolation During Slew Conditions
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Solution Overview
Problem
Chopper-stabilized amplifiers face challenges in becoming 'mux-friendly' for high-voltage applications, particularly in preventing damage from transients, reducing in-rush of input current, and ensuring quick response times in multiplexed measurement systems, which is exacerbated by their dual-path circuit topology and the need for input circuit protection.
Innovation Solution
The implementation of dual mux-friendly interface circuits and a settling-enhancer circuit in the chopper-stabilized amplifier to limit input voltage, block low-impedance paths during slew conditions, and stabilize compensation signals, respectively, enabling the amplifier to operate safely and efficiently in high-voltage environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the chopper-stabilized amplifier uses a dual-path circuit topology with chopper amplifier circuit, then the precision and accuracy are improved, but the in-rush of input current during slew condition increases
Solution Approach 1:
A second mux-interface circuit is introduced as an intermediary component between the first path and the chopper amplifier circuit. This circuit includes switching elements that can block the low-impedance path during slew conditions, preventing in-rush current while allowing normal signal transmission during steady-state operation.
Solution Approach 2:
The second mux-interface circuit dynamically changes its impedance state based on the operating condition. During slew conditions, it presents a high impedance to block current; during normal operation, it presents a low impedance to allow signal passage. This dynamic adaptation resolves the contradiction between precision enhancement and current surge prevention.
2Reliability
If the amplifier limits input voltage through first mux-interface circuit, then the protection from transient damage is improved, but the response time during slew condition increases
Solution Approach 1:
The first mux-interface circuit acts as a protective intermediary that limits input voltage to safe levels. By controlling the voltage presented to the amplifier core, it protects against transient damage while maintaining fast response times through proper switching element selection and circuit design.
Solution Approach 2:
The circuit changes the voltage parameter at the input stage by limiting it to safe levels during transient conditions. This parameter control allows the amplifier to respond quickly to valid signals while being protected from damaging transients, resolving the contradiction between reliability and speed.
3Measurement precision
If the chopper amplifier circuit is coupled to the first path, then the compensation signal is generated, but the low-impedance path causes measurement loading
Solution Approach 1:
The second mux-interface circuit serves as a mediator that controls the coupling between the first path and the chopper amplifier circuit. It enables the compensation signal to be generated by allowing the circuit connection during normal operation, while preventing measurement loading by blocking the low-impedance path during slew conditions when measurements are taken.
Data Source
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AI summary
A high-voltage chopper-stabilized amplifier can include two paths to compensate for non-ideal electrical parameters. A first path, leading to a primary input of the amplifier, may include a first mux interface circuit to limit voltages at the primary input of the amplifier. A second path, leading to an auxiliary input of the amplifier, may include a chopper amplifier circuit. Despite the first mux interface circuit, a slew condition on the first path may excite a current in the second path that can negatively affect the signal source. Accordingly, the disclosed amplifier further includes a second mux interface circuit that can decouple the second path while a slew condition. The second mux interface circuit is driven by a window floating comparator, which is supplied according to the voltages on primary input. A settling enhancer circuit keeps, during slew condition, certain nodes on the second path at a reference voltage.