Semiconductor Circuit Chopper Switch Noise Modulation
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Solution Overview
Problem
Conventional semiconductor circuits with a chopper switch connected only to the first stage suffer from inadequate noise modulation in the low frequency region, leading to unsuitable performance for applications requiring low noise, as the flicker noise of subsequent stages is not effectively modulated into higher frequency regions.
Innovation Solution
A semiconductor circuit with multiple amplifiers connected in series, where first and second chopper switches are synchronized with a common clock, and third and fourth chopper switches are synchronized with a different clock, incorporating phase compensation capacitors to avoid loading effects and improve power supply rejection ratio, allowing effective noise modulation across stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a chopper switch is connected only to the first stage amplifier, then the settling waveform is improved and glitches are reduced, but the flicker noise in the low frequency region is not effectively modulated
Solution Approach 1:
The patent divides the single chopper switch function into multiple chopper switches distributed across different amplifier stages. Specifically, it connects chopper switches to both the first stage amplifier and the second stage amplifier, allowing each stage to independently modulate its own flicker noise, thereby solving the problem of inadequate noise modulation when only the first stage has a chopper switch.
2Power
If a capacitor is connected inside the multistage configuration, then DC gain is improved, but the voltage settling is delayed due to the capacitor being seen as a load by the inverted node
Solution Approach 1:
The patent applies chopper switches to even-numbered stages (second stage) in addition to odd-numbered stages (first stage). This inversion pattern ensures that nodes inverted by chopper switches do not directly drive capacitors, thereby avoiding the capacitor being seen as a load that delays voltage settling, while still achieving the desired DC gain through the multistage configuration.
3Object-affected harmful factors
If chopper switches are connected to multiple amplifier stages, then flicker noise modulation is improved, but the circuit complexity increases
Solution Approach 1:
The patent selectively connects chopper switches to specific amplifier stages (first stage and second stage) rather than uniformly to all stages. This local application approach optimizes flicker noise modulation in critical low-frequency regions while avoiding unnecessary complexity in other parts of the circuit, achieving a balance between performance improvement and circuit simplicity.
Data Source
AI summary
A chopper switch is connected appropriately to multistage amplifiers.A semiconductor circuit includes a plurality of amplifiers that is connected in series and individually amplify and supply a signal on an input side thereof to an output side thereof. A first chopper switch is connected to an input side of a first amplifier connected first among the plurality of amplifies, and a second chopper switch is connected to an output side of the first amplifier. The first and second chopper switches act in synchronism with a first chopper clock. A third chopper switch is connected to an input side of a second amplifier connected second or later among the plurality of amplifiers, and a fourth chopper switch is connected to an output side of the second amplifier. The third and fourth chopper switches act in synchronism with a second chopper clock. A phase compensation capacitor is connected at one end thereof to an input portion of the third chopper switch.