Output Circuit Noise Tolerance via Gate Switching
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Solution Overview
Problem
Existing output circuits have low tolerance to noise transmitted from the output terminal due to noise being transmitted to the gate of the output transistor through parasitic capacitance, causing malfunctions in comparators.
Innovation Solution
An output circuit with a current control circuit and a switch circuit that controls the gate voltage of the output transistor based on the input signal, ensuring that the outflow and inflow of current is not affected by noise from the output terminal, using a voltage generating circuit and a capacitor to manage the gate voltage transitions and reduce noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate voltage is controlled by current sources connected to the output terminal, then the slew rate of the output signal is reduced and duty ratio is maintained, but noise from the output terminal is transmitted to the gate through parasitic capacitance causing malfunctions
Solution Approach 1:
The patent introduces a switch circuit as an intermediary between the output terminal and the gate of the output transistor. This switch circuit is controlled by the input signal and selectively connects or disconnects the gate from the output terminal, preventing noise transmission while maintaining the beneficial slew rate control function through the current sources.
Solution Approach 2:
The patent divides the control system into separate functional blocks: a current control circuit that generates control signals based on the input signal, and a switch circuit that physically isolates the gate from the output terminal. This segmentation allows the gate to be protected from noise while still receiving precise voltage control commands.
2Manufacturing precision
If multiple current sources are used to control gate voltage transitions, then the transition time is controlled accurately, but the circuit complexity increases
Solution Approach 1:
The patent employs dynamic control of the switch circuit based on the input signal state. The switch circuit transitions between connected and disconnected states, dynamically adjusting the gate's connection to the output terminal. This dynamic approach simplifies the overall circuit by eliminating the need for multiple continuously-operating current sources while maintaining precise transition control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The output circuit improves noise tolerance by ensuring that noise from the output terminal does not affect the operation of the current control and switch circuits, maintaining accurate duty ratio and reducing noise-induced malfunctions.
Implementation Method 1
noise gets into the output terminal, that noise is transmitted to the gate of the output transistor Qo through the parasitic capacitance between the drain and gate of the output transistor Qo
Data Source
AI summary
An output circuit in accordance with one embodiment of the present invention includes: an input terminal for receiving an input signal; an output transistor connected between a first power supply and an output terminal; a current control circuit connected to the input terminal and the output transistor for controlling current outflow and inflow for the gate of the output transistor based on the input signal; a voltage generating circuit connected to the first power supply; and a switch circuit coupled between the gate of the output transistor and the voltage generating circuit, the switch circuit having alternatively an on state and an off state thereof in response to the input signal; wherein the switch circuit becomes the off state when the potential difference between the gate of the output transistor and the first power supply becomes equal to or below a predetermine value regardless of the voltage level of the input signal.