CMOS Bandgap Reference Circuit With Two-Branch Current Mirrors
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Solution Overview
Problem
Existing bandgap voltage reference generators in CMOS technology require additional power sources and operational amplifiers, leading to increased current consumption, which is inefficient.
Innovation Solution
A circuit arrangement that generates a bandgap reference voltage using only two parasitic PNP bipolar substrate transistors with a reference-voltage generation module and current mirrors, eliminating the need for additional current consumption by integrating an analog buffer and adjustment resistances within the two branches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional power sources and operational amplifiers are used in bandgap voltage reference generators, then the precision and stability of reference voltage generation is improved, but current consumption increases
Solution Approach 1:
The patent extracts and eliminates unnecessary operational amplifiers and additional power sources from the bandgap voltage reference generator circuit. By removing these components that were not essential for the core function, the invention achieves significant current consumption reduction while preserving the reference voltage generation precision through optimized use of remaining components like parasitic bipolar transistors and current mirrors.
Solution Approach 2:
The patent makes existing components perform multiple functions. The parasitic bipolar transistors are used not only for their inherent bandgap reference function but also integrated with current mirror circuits that provide both voltage reference generation and current regulation functions simultaneously. This multi-functionality eliminates the need for separate operational amplifiers and reduces overall component count and power consumption.
2Adaptability or versatility
If parasitic PNP bipolar substrate transistors are used in CMOS technology, then the need for independent bipolar transistors is eliminated, but additional current consumption paths are created
Solution Approach 1:
The patent merges the bandgap voltage reference function with current mirror circuits in a unified two-branch architecture. By combining these functions into a single integrated structure using parasitic bipolar transistors, the invention eliminates separate current consumption paths and achieves efficient operation in CMOS technology without requiring additional independent power sources.
3Use of energy by moving object
If a simplified circuit with only two branches is used, then current consumption is reduced, but the complexity of achieving precise voltage reference may increase
Solution Approach 1:
The patent optimizes key circuit parameters including the aspect ratios of parasitic bipolar transistors, current mirror ratios, and resistance values in the two-branch configuration. By carefully selecting and adjusting these parameters, the simplified circuit achieves precise bandgap voltage reference generation without requiring complex additional components, thereby reducing current consumption while maintaining accuracy.
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
This solution reduces current consumption by approximately 33% while maintaining precision in generating the bandgap reference voltage, essential for analog and digital circuits like DRAMs and flash memories.
Implementation Method 1
the voltage V BE on the base-emitter junction of a bipolar transistor, with a negative temperature coefficient of approximately -2.2 mV/°C at room temperature
Implementation Method 2
the positive temperature coefficient of the thermal voltage V T, where V T = kT/q. The thermal voltage V T has a positive temperature coefficient of 0.085 mV/°C at room temperature
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A circuit arrangement for the generation of a bandgap voltage reference in CMOS technology, of the type that includes a circuit module (101; 101') for generation of a base-emitter voltage difference comprising at least one pair of PNP bipolar substrate transistors, which comprises a first bipolar substrate transistor (Q1) inserted in a first circuit branch (B1) that identifies a first current path (I1) from the supply voltage (Vdd) to ground (GND), and a second bipolar substrate transistor (Q2) inserted in a second circuit branch (B2) that identifies a second current path (12) from the supply voltage (Vdd) to ground (GND), said first bipolar substrate transistor (Q1) and second bipolar substrate transistor (Q2) being connected together via their base electrode, and the second transistor (Q2) having an aspect ratio (N) higher than that of the first transistor (Q), said circuit arrangement (100; 200; 200'; 200"; 300; 300'; 300"; 400; 400'; 400") comprising a first CMOS current mirror (102; 402; 402') of an n type, connected between said first branch (B1) and said second branch (B2) and connected via a resistance (R1) for adjustment of the bandgap reference voltage to the second bipolar transistor (Q1), a second CMOS current mirror (103; 103'; 403, 403") of a p type, connected between said first branch (B1) and said second branch (B2), said first current mirror (102; 402; 402') and second current mirror (103; 103'; 403, 403") being connected so that each current mirror repeats the current of the other. Said circuit module (101) for generation of a base-emitter voltage difference comprises just said first bipolar substrate transistor (Q1) inserted in the first circuit branch (B1) and said second bipolar substrate transistor (Q2) inserted in the second circuit branch (B2), the current that flows in said circuit arrangement (100; 200; 200'; 200"; 300; 300'; 300"; 400; 400'; 400") from the supply voltage (Vdd) to ground (GND) flowing only through said first bipolar substrate transistor (Q1) and said second bipolar substrate transistor (Q2).