Floating-Transconductor Preamplifier for Fast Low-Capacitance ADCs

The patent employs dynamic operation by dividing the preamplifier into two distinct phases: a sampling phase where switches connect input voltages to storage capacitors, and an amplification phase where the floating transconductor actively amplifies the stored voltages. This dynamic switching allows high-speed operation during amplification without requiring continuously high current, thereby reducing overall power consumption while maintaining high speed performance.

The preamplifier operates periodically by alternating between sampling and amplification phases controlled by non-overlapping clock signals. During the sampling phase, input voltages are captured; during the amplification phase, the floating transconductor provides high gain. This periodic operation allows the circuit to achieve high-speed amplification intermittently without sustaining high power consumption continuously, resolving the contradiction between speed and power usage.

The patent segments the preamplifier circuit into distinct functional blocks: input switches for voltage selection, storage capacitors for voltage holding, and a floating transconductor for amplification. This segmentation allows each component to be optimized independently - the storage capacitors can be sized appropriately for accuracy without requiring excessive current, while the floating transconductor provides the necessary high-speed amplification capability, thus resolving the contradiction between speed and accuracy.

The floating transconductor acts as an intermediary between the storage capacitors and the output, providing high-gain voltage amplification without requiring the input capacitors to be oversized. The transconductor converts the stored voltages on the capacitors into amplified output voltages, enabling high-speed operation while maintaining accuracy by keeping the input capacitor sizes moderate and well-controlled.

The patent merges the transconductor function with capacitive positive feedback into a single integrated floating transconductor structure. The feedback capacitors are directly connected to the transconductor outputs, combining the amplification and feedback functions in one unit. This integration reduces the number of separate components and interconnections needed, thereby reducing overall circuit complexity while achieving both low power consumption and high accuracy through the efficient feedback mechanism.

The floating transconductor serves multiple functions simultaneously: it provides voltage amplification, implements capacitive positive feedback, and operates in a dynamic switching mode to reduce power consumption. By making the transconductor multi-functional, the circuit achieves improved power efficiency and accuracy without proportionally increasing complexity, as the same core component performs multiple critical roles in the preamplifier operation.