Signal Shaping Circuit with Segmented Current Sources
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Solution Overview
Problem
Conventional preemphasis generating circuits in high-speed optical interconnects face challenges with high-power current supplying sources, leading to increased parasitic capacitance and power consumption, which limits their ability to operate at high speeds due to waveform deterioration and bandwidth limitations.
Innovation Solution
A signal shaping circuit that includes a main-signal amplifying circuit, a preemphasis generating circuit AC-coupled via condensers, and a current source within the main-signal amplifying circuit, allowing for reduced transistor current requirements and decreased parasitic capacitance, thereby enabling higher-speed operation with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high-power current supplying source is used in the conventional preemphasis generating circuit, then the circuit can provide sufficient current for both the main-signal amplifying circuit and the preemphasis generating circuit, but the transistor requires a high maximum rated current which increases parasitic capacitance and prevents high-speed operation
Solution Approach 1:
The patent divides the current supplying function into two separate current sources: one dedicated to the main-signal amplifying circuit and another to the preemphasis generating circuit. This segmentation allows each transistor to be sized appropriately for its specific function, with smaller transistors that have lower parasitic capacitance, thereby enabling high-speed operation while maintaining sufficient current supply capability for each subsystem.
2Speed
If separate current supplying sources are provided for the main-signal amplifying circuit and the preemphasis generating circuit, then the operation speed increases due to reduced parasitic capacitance, but the entire power consumption increases
Solution Approach 1:
The patent merges the power supply architecture by using a single common current source that serves both the main-signal amplifying circuit and the preemphasis generating circuit. This consolidation reduces the total number of transistors and current sources required, thereby decreasing overall power consumption while maintaining the speed benefits of dedicated current paths through proper circuit configuration and coupling capacitors.
3Use of energy by moving object
If a single current supplying source is used for both circuits, then power consumption is reduced, but the transistor must handle high current which increases parasitic capacitance and limits speed
Solution Approach 1:
The patent segments the current supply into two distinct sources, allowing each transistor to operate at lower current levels with correspondingly lower parasitic capacitance. This segmentation resolves the speed limitation imposed by high-current transistors while the unified power distribution architecture maintains acceptable power consumption levels.
Solution Approach 2:
The patent changes the current parameter distribution by allocating specific current levels to each circuit block through separate current sources. This parameter optimization allows transistors to be designed with lower current ratings and lower parasitic capacitance, enabling high-speed operation, while the overall system power consumption is managed through efficient current allocation and coupling mechanisms.
Data Source
AI summary
A signal shaping circuit that shapes a drive signal and includes a main-signal amplifying circuit that amplifies the drive signal; a preemphasis generating circuit that symmetrically emphasizes a rising portion and a falling portion of the drive signal; a current source that is provided in the main-signal amplifying circuit; and a condenser that couples the main-signal amplifying circuit and the preemphasis generating circuit.