Constant Current Circuit Temperature Compensation Using Poly-Silicon Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In CMOS processing, conventional constant current circuits face issues with temperature stability due to the interaction between positive temperature characteristics of heat voltage and resistance, especially when using poly-silicon resistances with negative temperature characteristics, which can enhance rather than offset temperature effects on current.
Innovation Solution
A constant current circuit is designed with a temperature compensation circuit in parallel to the serial connection circuit, utilizing poly-silicon resistances with negative temperature characteristics and diode structures to generate a current that offsets the positive temperature characteristics of the heat voltage, ensuring the output current is less affected by temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If poly-silicon resistance is used in CMOS processing, then the circuit can be manufactured as a semiconductor integrated circuit, but the resistance element has negative temperature characteristics which enhance rather than offset temperature effects on current
Solution Approach 1:
The current generation circuit is divided into two parallel paths: a first path with a first resistance element (positive temperature coefficient) and a second path with a second resistance element (negative temperature coefficient). Each path generates a current component with opposite temperature characteristics, which are then combined to produce an output current with improved temperature stability.
Solution Approach 2:
The invention changes the temperature characteristic parameter of resistance elements by using two different types: poly-silicon resistance (negative temperature coefficient) and diffused resistance (positive temperature coefficient). By adjusting the ratio of current components from these different resistance types, the overall temperature characteristic of the output current can be controlled and optimized.
2Reliability
If a resistance element with positive temperature characteristics is used to offset heat voltage temperature characteristics, then temperature stability can be achieved, but this approach fails when poly-silicon resistance with negative temperature characteristics is used in CMOS processing
Solution Approach 1:
The invention converts the harmful negative temperature characteristic of poly-silicon resistance into a beneficial feature. Instead of trying to eliminate or avoid this characteristic, the circuit design utilizes it by creating a parallel path where the poly-silicon resistance generates a current component with negative temperature coefficient, which compensates for the positive temperature coefficient from other components.
3Productivity
If equivalent currents flow through MOSFETs in a current mirror circuit, then constant current can be generated, but temperature variations cause changes in the output current
Solution Approach 1:
The current mirror circuit is segmented into multiple parallel current generation paths, each with different temperature characteristics. The first path uses a first resistance element to generate a current component with positive temperature coefficient, while the second path uses a second resistance element to generate a current component with negative temperature coefficient. These segmented current components are combined to achieve temperature stability.
Solution Approach 2:
The invention creates a composite current by combining current components from two different resistance materials with opposite temperature coefficients. This composite approach is analogous to using composite materials in engineering, where combining materials with different properties creates a system with superior overall performance - in this case, temperature-stable current output.
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 circuit effectively suppresses changes in output current due to temperature variations by balancing the current components with negative and positive temperature characteristics, resulting in a stable constant current output.
Implementation Method 1
a first resistance element (R1) having positive temperature characteristics and a second resistance element (R2) having negative temperature characteristics
Implementation Method 2
a first diode structure (D1) and a second diode structure (D2)
Data Source
AI summary
In CMOS processing, there may be a case in which a resistance element, such as a poly-silicon resistance, or the like, may be formed which has negative temperature characteristics. In a constant current circuit using this resistance element, a constant current output less affected by the influence of varying temperature is obtained. To a load-side path of a current mirror circuit, a serial connection circuit and a temperature compensation circuit are arranged in parallel each other. The serial connection circuit includes a transistor Q1, a resistance element R1 and a bipolar transistor Q6 and flows a current I1 having positive temperature characteristics. The temperature compensation circuit includes a transistor Q8 and a resistance element R2 and flows a current I2 having negative temperature characteristics. A constant current output based on the sum current I of the currents I1 and I2 is obtained.