Amplifier Input Stage Switching for Wide Range and Low Capacitance
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Solution Overview
Problem
Existing amplifiers face limitations in achieving a wide input range and low input capacitance, which affects their performance and power consumption.
Innovation Solution
The amplifier input stage includes a pair of input terminals, n-type and p-type input transistors, and isolation switches, with a control circuit that selectively uses these transistors based on the common-mode voltage to decouple unused transistors, reducing input capacitance and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple input transistors (n-type and p-type) are connected to input terminals, then input range is extended, but input capacitance increases
Solution Approach 1:
The patent employs isolation switches that dynamically connect or disconnect input transistors from the input terminals based on the common-mode voltage level. When a transistor is not needed for operation, its isolation switch opens to decouple it from the input terminals, effectively removing its capacitance from the input. This dynamic switching mechanism allows the amplifier to maintain low input capacitance while providing access to both n-type and p-type transistors for extended input range when needed.
2Object-affected harmful factors
If isolation switches are used to decouple unused transistors, then input capacitance is reduced, but device complexity increases
Solution Approach 1:
The isolation switches serve multiple functions: they decouple unused input transistors to reduce input capacitance, they protect the input terminals from unwanted transistor effects, and they enable the amplifier to operate with different transistor types based on voltage conditions. By making the isolation switches multi-functional, the patent reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving capacitance reduction.
3Adaptability or versatility
If control circuit is added to select transistors based on common-mode voltage, then input range performance is improved, but power consumption increases
Solution Approach 1:
The control circuit monitors the common-mode voltage parameter and uses it to determine which input transistors should be active. By basing the selection on the existing voltage parameter rather than requiring additional sensing circuits, the patent minimizes the power consumption of the control mechanism while still achieving adaptive transistor selection that extends the input range.
Data Source
AI summary
Amplifiers with wide input range and low input capacitance are provided. In certain embodiments, an amplifier input stage includes a pair of input terminals, a pair of n-type input transistors, a first pair of isolation switches connected between the input terminals and the n-type input transistors, a pair of p-type input transistors, and a second pair of isolation switches connected between the input terminals and the p-type input transistors. The amplifier input stage further includes a control circuit that determines whether to use the n-type input transistors and/or the p-type input transistors for amplification based on a detected common-mode voltage of the input terminals. The control circuit opens the first pair of isolation switches to decouple the input terminals from the n-type input transistors when unused, and opens the second pair of isolation switches to decouple the input terminals from the p-type input transistors when unused.