CMOS Voltage Reference Circuit Without Op-Amps for Low Power
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Solution Overview
Problem
Conventional voltage reference circuits face challenges in achieving accurate temperature compensation while maintaining low power consumption and cost-effectiveness, particularly in low voltage applications, due to issues such as operational amplifier offset, process variability, and increased complexity.
Innovation Solution
A voltage reference circuit design that combines proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) currents using a multi-stage common-source amplifier and current mirror circuits, excluding operational amplifiers and employing field-effect transistors (FETs) to generate a stable reference voltage, with a feedback loop for improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional reference circuits use operational amplifiers and bipolar junction transistors to achieve temperature compensation, then temperature coefficient is improved, but power consumption increases
Solution Approach 1:
The patent extracts and eliminates the operational amplifier from the reference circuit, replacing it with a simplified transistor-based architecture. This removal of the power-hungry operational amplifier directly reduces power consumption while maintaining temperature compensation functionality through alternative circuit arrangements using transistors Q61, Q62, Q71, and Q72.
Solution Approach 2:
The patent substitutes the operational amplifier (an active electronic component with high power consumption) with a passive transistor-based temperature compensation mechanism. The transistors directly generate and combine PTAT and CTAT currents to achieve temperature independence without requiring the operational amplifier's active control, thereby reducing power consumption.
2Measurement precision
If conventional reference circuits use operational amplifiers for temperature compensation, then accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent removes the operational amplifier from the circuit architecture, significantly simplifying the circuit structure. The temperature compensation function is achieved through a more straightforward transistor-based current combination approach, reducing the number of components and interconnections while maintaining accuracy.
Solution Approach 2:
Instead of using an operational amplifier to actively control and adjust currents for temperature compensation, the patent inverts the approach by using transistors to passively generate and combine PTAT and CTAT currents that naturally compensate for temperature effects. This inverted architecture achieves the same accuracy goal with simpler circuitry.
3Manufacturing precision
If conventional reference circuits use additional process masks for manufacturing, then manufacturing precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent designs the reference circuit to be fully compatible with standard CMOS fabrication processes, allowing the same process masks used for general CMOS manufacturing to be used for the reference circuit. The circuit uses only standard CMOS components (transistors and resistors) that can be manufactured using existing process masks, eliminating the need for additional specialized masks while maintaining manufacturing precision.
Data Source
AI summary
A voltage reference circuit includes a first circuit block configured to generate a proportional to absolute temperature current, the first circuit block comprising a current mirror amplifier, a second circuit block coupled to the first circuit block and configured to generated a complimentary to absolute temperature current, and a third circuit block coupled to both the first circuit block and the second circuit block. The second circuit block includes a multi-stage common-source amplifier. The third circuit block is configured to combine the proportional to absolute temperature current and the complimentary to absolute temperature current to generate a reference voltage at an output of the voltage reference circuit.