Input Buffer Reference Voltage Compensation for Supply Variation
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Solution Overview
Problem
Semiconductor circuits face challenges in maintaining stable output characteristics due to variations in supply voltages, particularly when operating with both internal and external supply voltages.
Innovation Solution
A voltage generation circuit and input buffer configuration that includes diode-connected transistors and a compensation circuit to generate reference voltages, which are insensitive to variations in internal supply voltage levels, ensuring stable output signals regardless of supply voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the internal supply voltage level rises, then the threshold voltage of the second transistor rises, but the second reference voltage level varies significantly
Solution Approach 1:
The patent implements a feedback mechanism where the third transistor's gate is controlled by a reference voltage that is fed back to adjust the second reference voltage generation. This feedback loop compensates for threshold voltage variations of the second transistor caused by internal supply voltage changes, thereby stabilizing the second reference voltage level despite variations in operating conditions
Solution Approach 2:
The patent changes the operating parameters of the transistor circuit by introducing a third transistor configured with its gate connected to a stable reference voltage source. This parameter change (adding the third transistor with fixed gate voltage) compensates for the threshold voltage drift of the second transistor, maintaining stable second reference voltage output even when internal supply voltage varies
2Adaptability or versatility
If the input buffer operates with different types of supply voltages, then it can adapt to various operating conditions, but the output characteristic becomes sensitive to supply voltage variations
Solution Approach 1:
The patent introduces a second reference voltage as an intermediary element between the internal supply voltage and the output signal generation. This second reference voltage acts as a mediator that is less sensitive to supply voltage variations, thereby decoupling the output characteristic sensitivity from the supply voltage fluctuations while maintaining adaptability to different supply voltage types
Solution Approach 2:
The patent creates a replica or copy of the reference voltage generation path through the second and third transistors, where the third transistor copies the reference voltage function with improved stability characteristics. This copied reference voltage path provides a more stable reference that is less affected by supply voltage variations, enabling reliable operation across different supply voltage conditions
Data Source
AI summary
A voltage generation circuit may include: a first transistor coupled to an internal supply voltage terminal, and configured as a diode-connected transistor; a second transistor coupled to the first transistor and configured as a diode-connected transistor; and a third transistor coupled between the second transistor and a ground voltage terminal, and configured to operate according to a first reference voltage generated based on an external supply voltage. The voltage generation circuit may limit a variation in level of a second reference voltage which is generated through a drain terminal of the second transistor as a threshold voltage of the second transistor rises according to a rise in level of the internal supply voltage.