Reference Voltage Circuit With Feedback BJT Current Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Integrated circuits face inaccuracies in reference voltage generation due to temperature variations, leading to potential malfunctions, as the current characteristics of bipolar junction transistors (BJTs) change during the semiconductor process, affecting the precision of the reference voltage.
Innovation Solution
A reference voltage generating circuit is designed with operational amplifiers, transistors, and variable resistors to adjust the current characteristics of BJTs, ensuring the reference voltage remains accurate despite process variations, using a method that involves sensing changes in current characteristics and adjusting resistance values to maintain optimal emitter current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the current characteristics of BJT are used directly in reference voltage generation, then the circuit structure remains simple, but the reference voltage precision deteriorates due to process variations
Solution Approach 1:
The patent implements a feedback mechanism where the operational amplifier continuously monitors the voltage at the first node and adjusts the control signal to the first transistor accordingly. This closed-loop feedback system compensates for process variations in BJT current characteristics, maintaining precise reference voltage output despite manufacturing tolerances in the transistor parameters.
Solution Approach 2:
The patent dynamically adjusts the operating parameters of the first transistor by varying its control signal through the operational amplifier. By changing the operating point parameters (such as emitter current) of the BJT based on feedback from the voltage measurement, the system optimizes the reference voltage precision while accounting for process variations without requiring a completely complex circuit redesign.
2Manufacturing precision
If variable resistors are added to adjust current characteristics, then the reference voltage accuracy improves, but the device complexity increases
Solution Approach 1:
The operational amplifier in the patent serves multiple functions simultaneously: it acts as a voltage follower to buffer the reference voltage, as a comparator to detect voltage deviations, and as a feedback controller to adjust the transistor operating point. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while achieving improved reference voltage accuracy through active compensation.
3Measurement precision
If the first transistor current is adjusted to compensate for process variations, then the reference voltage precision is enhanced, but the circuit requires additional control mechanisms
Solution Approach 1:
The operational amplifier creates a negative feedback loop that automatically adjusts the first transistor's current by comparing the actual voltage at the first node with the desired reference voltage. This self-regulating feedback mechanism eliminates the need for external manual adjustment or complex control circuits, as the system autonomously compensates for process variations through the feedback signal, thereby enhancing precision without proportionally increasing control mechanism complexity.
Data Source
AI summary
A reference voltage generating circuit includes: an operational amplifier including a first input terminal connected to a first node and a second input terminal connected to a second node; a first transistor connected between a ground terminal and the first node, wherein a first current flows in the first transistor; a second transistor connected to the ground terminal; and a first variable resistor connected between the second transistor and the second node, wherein the first variable resistor has a first resistance value for adjusting the first current, based on a change in a current characteristic of the first transistor caused by a variation in a process of forming the first transistor. The reference voltage generating circuit provides a reference voltage, based on a voltage of the first node and a voltage across the first variable resistor.