Bias-Controlled Output Buffer Switching for Low Noise and Through Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-driving-capacity output buffers face issues with increased power consumption, power supply noise, and through current due to larger transistor sizes, particularly in driving loads with large load capacities.
Innovation Solution
An output buffer circuit with a bias circuit generating bias voltages and transistors with controlled current driving capabilities to manage transistor states, reducing through current and noise generation while maintaining high-speed response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If larger transistor sizes are used in high-driving-capacity output buffers, then driving capability is improved, but power consumption and through current increase
Solution Approach 1:
The output buffer is divided into a buffer part with large transistors for high driving capability and a pre-buffer part with small transistors for signal preparation. This segmentation allows the large transistors to be activated only when needed, reducing overall power consumption while maintaining high driving capability when required.
Solution Approach 2:
The pre-buffer part performs preliminary signal preparation using small transistors before the main buffer part is activated. This preliminary action ensures that when the large transistors in the buffer part are turned on, the input signal is already prepared, reducing the time they remain in the on-state and thereby reducing power consumption and through current.
2Productivity
If larger transistor sizes are used in high-driving-capacity output buffers, then driving capability is improved, but power supply noise increases
Solution Approach 1:
By segmenting the buffer into pre-buffer and buffer parts with different transistor sizes, the large transistors that generate noise are activated only when high driving capability is needed, while the small transistors handle routine signal preparation, thereby reducing overall noise generation.
Solution Approach 2:
The pre-buffer part performs preliminary signal preparation using small transistors, so that when the main buffer part with large transistors is activated, the signal transition is already prepared, reducing the duration of high-current flow and thereby reducing power supply noise.
3Object-generated harmful factors
If the transition from ON state to OFF state is made slower to prevent through current, then through current is suppressed, but response speed decreases
Solution Approach 1:
The pre-buffer part performs preliminary signal preparation and controls the timing of transistor activation. By preparing the signal in advance through the pre-buffer, the main buffer transistors can switch more quickly without causing significant through current, as the signal transition is already initiated by the pre-buffer part.
Solution Approach 2:
The pre-buffer part acts as an intermediary between the input signal and the main buffer part. It mediates the signal transition and controls the timing of the main buffer transistor activation, allowing for faster response while minimizing through current by ensuring proper sequencing of transistor switching.
Data Source
AI summary
The disclosure includes: a bias circuit generating first and second bias voltages; a first conductivity type first transistor supplying a first power source voltage to a first node according to the input signal; a second conductivity type second transistor supplying a second power source voltage to a second node according to the input signal; a second conductivity type third transistor receiving the first bias voltage by gate, with source and drain connected to the second and first nodes; a first conductivity type fourth transistor receiving the second bias voltage by gate, with source and drain connected to the first and second nodes; a first conductivity type fifth transistor supplying the first power source voltage to an output terminal according to voltage at the first node; and a second conductivity type sixth transistor supplying the second power source voltage to the output terminal according to voltage at the second node.