Output Buffer Circuit With Variable Resistors for Rise-Fall Timing
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Solution Overview
Problem
Existing output buffer circuits require complex and multiple adjustments to set the rise and fall times of output signals due to their dependence on the drive capability of preceding stages, making it difficult to achieve desired output characteristics.
Innovation Solution
An output buffer circuit with P-type and N-type transistors and variable resistor circuits that adjust resistance values based on control signals, allowing independent control of rise and fall times without altering the drive capabilities of preceding stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the output characteristic is adjusted by changing the drive capability of the circuit in the preceding stage, then the output characteristics such as rise time and fall time can be adjusted, but complex and multiple adjustments are required
Solution Approach 1:
The patent introduces variable resistor circuits that can independently adjust resistance values to control rise time and fall time. By changing the resistance parameter in the output buffer circuit rather than adjusting the drive capability of the preceding stage, the system achieves precise output characteristic control with simpler, more direct adjustment mechanisms.
Solution Approach 2:
The patent divides the output buffer circuit into separate variable resistor circuits for controlling rise time and fall time independently. This segmentation allows each parameter to be adjusted separately without affecting the other, eliminating the need for complex multiple adjustments of the preceding stage drive capability.
2Adaptability or versatility
If multiple MOSFET circuits are arranged in parallel with selective high impedance, then output characteristics can be adjusted, but the output characteristic is influenced by the output waveform of the preceding stage circuit
Solution Approach 1:
The patent introduces variable resistor circuits as intermediary elements between the MOSFET circuits and the output node. These resistors act as mediators that decouple the output characteristics from the preceding stage's output waveform, allowing independent control of rise and fall times while maintaining stability regardless of preceding stage variations.
3Speed
If the drive capability of the preceding stage is adjusted to control output characteristics, then rise time and fall time can be optimized, but through-current increases
Solution Approach 1:
The patent changes the control parameter from drive capability to resistance value in the output buffer circuit. By adjusting the resistance of variable resistors rather than increasing the drive capability of the preceding stage, the system achieves fast rise and fall times without the side effect of increased through-current and energy loss.
Data Source
AI summary
An output buffer circuit includes an output node, a P-type transistor, an N-type transistor, and a first variable resistor circuit provided in a signal path between a drain of one of the P-type transistor and the N-type transistor and the output node.