Low Voltage Bandgap Reference Circuit Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As microelectronics trends toward smaller devices with lower supply voltages, maintaining headroom for bandgap voltage references becomes challenging, especially when supply voltages approach the nominal base-emitter voltages of silicon bipolar transistors, leading to output voltage errors due to transistors operating outside the saturation region.
Innovation Solution
A low voltage bandgap reference circuit is designed using current generators with feedback circuits to produce currents proportional to base-emitter voltages of transistors, mirroring these currents through resistors to generate a temperature-stable reference voltage, allowing operation at low supply voltages such as 0.81V by adjusting proportionality constants and resistor values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If supply voltage is reduced to support smaller device sizes, then device miniaturization is achieved, but headroom for bandgap voltage reference operation deteriorates
Solution Approach 1:
The bandgap reference circuit is segmented into multiple independent current generators (first current generator with first diode and first resistance, second current generator with second diode and second resistance). Each segment operates independently with its own feedback control, allowing the overall circuit to function reliably at lower supply voltages by distributing the voltage headroom requirements across multiple segments rather than requiring one large voltage drop.
2Power
If supply voltage approaches base-emitter voltage, then voltage headroom is reduced, but transistor saturation operation becomes difficult to maintain
Solution Approach 1:
Feedback circuits are implemented in each current generator to sense the voltage across the respective resistance and adjust the transistor gate voltages accordingly. This feedback mechanism ensures that transistors maintain saturation operation even when supply voltage is reduced, by dynamically compensating for voltage drops and preventing transistors from entering the triode region.
Solution Approach 2:
The circuit uses proportional relationships between currents and voltages with adjustable proportionality constants. By changing the resistance values and proportionality constants, the circuit can adapt to different supply voltage levels while maintaining proper transistor operation. The feedback circuits adjust operating parameters dynamically to keep transistors in saturation despite reduced voltage headroom.
Data Source
AI summary
In accordance with an embodiment, a reference voltage generator includes a first current generator and a second current generator. The first current generator is configured to produce a first current proportional to a current through a first diode connected in series with the first resistance coupled between a first voltage and a second voltage, such that the first current is produced according to a first proportionality constant. The second current generator is configured to produce a second current proportional to a current through a second diode connected in series with the second resistance coupled between the first voltage and the second voltage, such that the second current is produced according to a second proportionality constant. The reference voltage generator further includes a reference resistor coupled to the first and second current generators and to and output of the reference voltage generator.