Current Mirror Reference Current Source for High PSRR Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor structures shrink, the power supply rejection ratio (PSRR) of reference currents in integrated circuits decreases, making it challenging to stably supply reference currents with simple structures that are resistant to power supply and temperature fluctuations.
Innovation Solution
A reference current source is designed with a structure that includes a diode-connected first transistor, a second diode-connected transistor, and resistors, forming current mirrors and voltage-current conversion circuits to stabilize the reference current, eliminating the need for complex temperature compensation circuits and activation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the semiconductor structure size is shrunk to reduce manufacturing cost and increase integration, then the power supply rejection ratio (PSRR) of the reference current decreases, making it more sensitive to power supply fluctuations
Solution Approach 1:
The patent introduces a current mirror circuit as an intermediary mechanism between the power supply and the reference current. The current mirror (comprising transistors Q1-Q4 and resistors R1-R2) acts as a buffer that isolates the reference current from power supply fluctuations, thereby maintaining high PSRR even in scaled semiconductor structures where direct connection would be vulnerable
Solution Approach 2:
The patent utilizes temperature-dependent parameter changes of semiconductor devices to compensate for PSRR degradation. By designing the current mirror with specific transistor sizing ratios and resistor values, the circuit exploits the temperature characteristics of MOS transistors to maintain stable reference current output despite power supply variations and scaling effects
2Reliability
If a complex temperature compensation circuit is added to improve temperature stability of the reference current, then the reference current stability improves, but the device complexity increases
Solution Approach 1:
The current mirror circuit performs multiple functions simultaneously: it provides current buffering, temperature compensation, and power supply rejection. The same transistors and resistors that form the current mirror also serve as the temperature compensation mechanism, eliminating the need for separate compensation circuits and reducing overall device complexity
Solution Approach 2:
The patent merges the temperature compensation function with the current mirror structure. The resistors R1 and R2 are integrated into the current mirror path, and the transistors Q1-Q4 serve both as current copying elements and as temperature-sensitive devices that automatically compensate for thermal drift, combining multiple functions into a single unified circuit
Data Source
AI summary
A reference current source includes a reference current path, a first output current path and a second output current path. The reference current path includes a diode-connected first transistor, a diode-connected second transistor, and a first resistor that are connected in series between a first fixed potential and a second fixed potential. The first output current path includes a third transistor having a gate connected to a gate of the second transistor, forming a current mirror together with the second transistor, and a second resistor interposed between the third transistor and the first fixed potential. The second output current path includes a voltage-current conversion circuit to which a potential of a third node between the third transistor and the second resistor in the first output current path is applied and through which a reference current flows.