Output Filter Circuit for High-Frequency Voltage Spike Suppression
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Solution Overview
Problem
Unwanted voltage spikes or bumps occur on the output of electronic circuits due to high frequency coupling effects, leading to signal integrity issues and erroneous signals in connected circuits.
Innovation Solution
A filter circuit comprising a capacitor and transistors configured as a high pass filter, connected between a supply voltage and a transistor, to attenuate undesired voltage spikes by operating as a high pass filter and preventing voltage coupling to external capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the supply voltage ramp rate is increased to improve circuit response speed, then the circuit operation speed is improved, but high frequency coupling effects arise leading to unwanted voltage spikes and signal integrity degradation
Solution Approach 1:
A filter circuit comprising a capacitor and transistors is introduced as an intermediary component between the supply voltage source and the CMOS output driver. This filter circuit selectively attenuates high frequency voltage spikes while allowing the beneficial supply ramp to pass through, thereby mediating between the conflicting requirements of fast response speed and signal integrity
Solution Approach 2:
The filter circuit changes the frequency domain parameters of the supply voltage by attenuating high frequency components. The capacitor and transistor combination creates a frequency-dependent impedance that selectively reduces the amplitude of high frequency voltage spikes while maintaining the integrity of the supply ramp, thus resolving the contradiction between speed and signal quality
2Object-affected harmful factors
If synchronisation of supply voltage turn on with second circuit turn on is implemented to reduce bump effects, then voltage spikes are reduced, but additional timing signals are required and circuit complexity increases
Solution Approach 1:
The harmful high frequency bump effects are extracted and removed from the supply voltage waveform by the filter circuit before reaching the output driver. This extraction approach eliminates the need for complex synchronisation timing signals while still achieving the goal of reducing voltage spikes, thereby reducing overall system complexity
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 filter circuit effectively reduces the amplitude of voltage spikes and minimizes high frequency coupling effects, ensuring stable signal integrity by maintaining a constant voltage at the output during supply ramp-up.
Implementation Method 1
the first transistor, the second transistor and the capacitor operate as a high pass filter
Implementation Method 2
a capacitor connected between a supply voltage and a first transistor wherein the first transistor is arranged as a diode connected transistor
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
This disclosure relates to a filter circuit for an output stage of electronic circuit, the filter comprising: a capacitor connected between a supply voltage and a first transistor wherein the first transistor is arranged as a diode connected transistor; a second transistor connected to the first transistor such that the first and second transistors are arranged as a current mirror; wherein the capacitor is connected to the first and second transistors and configured and arranged such that during operation the first transistor, the second transistor and the capacitor operate as a high pass filter.