Constant Voltage Generator Feedback Circuit for High-Frequency Noise Offset
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In constant voltage generator circuits with differential amplifier feedback circuits, high-frequency noise outside the loop frequency band causes amplitude differences between inputs, leading to DC offset and malfunction, especially when phase compensation capacitance is used.
Innovation Solution
Incorporating a resistor in series with the phase compensation capacitance in the feedback circuit to match noise amplitudes between the inverting and non-inverting inputs, preventing DC offset generation by ensuring equal noise propagation to both inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If phase compensation capacitance is used in the feedback circuit to ensure stability, then feedback system stability is improved, but noise immunity deteriorates when high-frequency noise components are superimposed on substrate voltage potential, power supply, or output
Solution Approach 1:
A noise cancellation circuit is introduced as an intermediary system that receives substrate voltage potential, power supply voltage, and output voltage as inputs, processes these signals to generate noise components, and subtracts them from the differential amplifier inputs. This mediator actively cancels the harmful noise effects while preserving the beneficial phase compensation capacitance for stability.
Solution Approach 2:
The noise cancellation circuit performs preliminary anti-action by proactively generating and subtracting noise components before they can cause DC offset in the differential amplifier. The circuit predicts the noise based on substrate voltage, power supply voltage, and output voltage, and applies the opposite signal to prevent the harmful effect.
2Measurement precision
If high-frequency noise components are inputted outside the loop frequency band, then the differential amplifier generates DC offset, but the feedback circuit cannot suppress this noise as it is outside its frequency response range
Solution Approach 1:
The noise cancellation circuit acts as an intermediary that handles high-frequency noise components outside the feedback loop's frequency response range. It processes these out-of-band noise signals separately and subtracts them from the differential amplifier inputs, preventing DC offset generation while allowing the main feedback circuit to focus on its primary frequency range.
Data Source
AI summary
A constant voltage generator circuit is provided with an operational amplifier including a feedback circuit having a first resistor, and an output transistor. The operational amplifier generates a feedback voltage generated by dividing an output voltage between an output terminal and a substrate voltage potential of the constant voltage generator circuit by the first resistor and a second resistor. Then, the operational amplifier is configured to amplify a voltage potential difference between a predetermined reference voltage and the feedback voltage and to output a control voltage. The output transistor controls an output voltage based on the control voltage from the operational amplifier, and the feedback circuit is further configured to superimpose high-frequency noise components from the substrate voltage potential onto the feedback voltage.