Current-Mode Programmable Reference Circuits for Low Voltage Operation
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Solution Overview
Problem
Conventional bandgap reference circuits face challenges in operating at reduced voltage levels due to limited voltage head-room, making them unsuitable for deep sub-micron CMOS circuit implementations, which require new current-mode reference architectures.
Innovation Solution
The development of current-mode programmable reference circuits using floating-gate transistors, which include differential amplifiers and resistors to generate a constant current and adjustable reference voltage, allowing for precise tuning of threshold voltages and operation at low voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional bandgap reference circuits are used, then reference voltage stability is achieved, but voltage head-room requirement increases
Solution Approach 1:
The patent replaces the conventional voltage-mode bandgap reference architecture with a current-mode reference architecture. This substitution fundamentally changes the operating principles from voltage-based to current-based references, enabling operation at lower voltage levels while maintaining reference stability. The current-mode approach uses current mirrors and transconductance amplifiers instead of voltage dividers and operational amplifiers, thereby reducing voltage head-room requirements.
Solution Approach 2:
The patent changes the fundamental operating parameter from voltage to current. By deriving the reference output as a current rather than a voltage, and by using current-mode building blocks throughout the circuit, the design achieves both low voltage operation and stable reference output. The reference current is generated through careful biasing and current mirroring techniques that are insensitive to voltage variations.
2Measurement precision
If voltage-mode architectures are used, then reference accuracy is improved, but operating voltage level increases
Solution Approach 1:
The patent substitutes voltage-mode circuitry with current-mode circuitry throughout the reference architecture. Current-mode operational amplifiers, current mirrors, and transconductance stages replace their voltage-mode counterparts. This substitution maintains high accuracy through precise current matching and mirroring while enabling operation at reduced voltage levels suitable for deep sub-micron CMOS processes.
3Stability of the object's composition
If conventional bandgap circuits are implemented, then reference stability is maintained, but adaptability to deep sub-micron CMOS reduces
Solution Approach 1:
The patent changes the fundamental operating mode from voltage-mode to current-mode, which inherently better suits deep sub-micron CMOS technology. Current-mode circuits are more compatible with the lower voltage supplies and higher frequency characteristics of modern CMOS processes. The design uses current mirrors and biasing schemes that are particularly well-suited to CMOS implementation, maintaining reference stability while achieving excellent adaptability to deep sub-micron technologies.
Data Source
AI summary
A circuit includes a first current path comprising a first floating-gate transistor having a programmable threshold voltage, a second current path, and a differential amplifier. The second current path includes a second floating-gate transistor having a programmable threshold voltage and a resistor. The differential amplifier includes a first input coupled to the first current path, a second input coupled to the second current path, and an output configured to control a reference current path.