Band Gap Reference Circuit with Cascode Current Mirrors for Low Voltage Operation
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Solution Overview
Problem
Existing reference signal generating circuits face challenges in operating at low voltages while maintaining high accuracy and stability, especially when packaged in chips, as they are often dependent on power source and temperature fluctuations, and require complex bias circuits that occupy large areas and are difficult to optimize.
Innovation Solution
A reference signal generating circuit using a band gap reference main unit with cascode current mirror units and bias voltage generating units to stabilize the operation and generate a reference signal, incorporating a diode and resistance structure that cancels temperature dependency and allows for low-voltage operation without external bias voltage, thus ensuring high accuracy and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reference signal generating circuit is designed to operate at low voltage, then power source voltage requirement is reduced, but accuracy and stability deteriorate due to increased dependency on power source and temperature fluctuations
Solution Approach 1:
The patent employs multiple feedback mechanisms through bias voltage generating units that continuously monitor and adjust the operating points of cascode current mirror units. This feedback system compensates for power source voltage variations and temperature fluctuations, maintaining reference signal accuracy even at low operating voltages. The loop structure ensures that any deviation from the desired reference level triggers corrective action, thereby preserving reliability while enabling low-voltage operation.
Solution Approach 2:
The circuit dynamically adjusts critical parameters including bias voltages, current levels, and transistor operating points to optimize performance across varying power source conditions. By changing these parameters in response to input voltage levels and temperature, the circuit maintains stable reference signal generation despite operating at reduced voltages, thus resolving the contradiction between low voltage requirement and accuracy maintenance.
2Measurement precision
If cascode current mirror units are used to improve accuracy, then reference signal precision is improved, but the circuit requires higher power source voltage which conflicts with low-voltage operation requirement
Solution Approach 1:
The patent implements dynamic bias voltage adjustment mechanisms that adapt the operating characteristics of cascode current mirror units based on the available power source voltage. The bias voltage generating units dynamically modify gate-source voltages and current levels to maintain optimal cascode operation across a wide voltage range. This dynamic adaptation allows the circuit to preserve the high accuracy benefits of cascode structures while functioning at low voltages, as the operating point is continuously optimized rather than fixed.
Solution Approach 2:
The circuit changes critical operating parameters including current levels, voltage drops across transistor stacks, and bias point locations to enable cascode current mirror operation at reduced voltages. By adjusting these parameters, the maintain the precision advantages of cascode structures (which provide high output impedance and accurate current copying) while adapting to low-voltage constraints. The parameter changes ensure that the voltage headroom required for cascode operation is minimized while preserving 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
The proposed solution achieves stable and accurate reference signal generation at low voltages with reduced dependency on power source and temperature fluctuations, ensuring high accuracy and compact chip packaging by integrating bias voltage generation and using a diode-resistance structure to cancel temperature effects.
Implementation Method 1
a band gap reference main unit 1, a first bias voltage generating unit 2, a second bias voltage generating unit 3, and an output unit 4. The band gap reference main unit 1 includes a first cascode current mirror circuit 5, a second cascode current mirror circuit 6, and a basic circuit 7
Implementation Method 2
incorporating a diode and resistance structure that cancels temperature dependency
Implementation Method 3
a first cascode current mirror circuit 5, a second cascode current mirror circuit 6
Implementation Method 4
The first cascode current mirror circuit (5) includes a first plurality of conductive-type transistors (MP0 to MP3). The second cascode current mirror circuit (6) includes a second plurality of conductive-type transistors (MN0 to MN3)
Implementation Method 5
a first bias voltage generating unit 2 that copies a current flowing through the first cascode current mirror unit to generate a bias voltage of the second cascode current mirror unit; a second bias voltage generating unit 3 that copies a current flowing through the second cascode current mirror unit to generate a bias voltage of the first cascode current mirror unit
Data Source
AI summary
According to an aspect of the invention, a reference signal generating circuit includes a band gap reference main unit that includes a first cascode current mirror unit having a plurality of first conductive-type transistors; a second cascode current mirror unit having a plurality of second conductive-type transistors; a reference unit that uses a band gap to generate a reference signal; a first bias voltage generating unit that generates a bias voltage of the second cascode current mirror unit; a second bias voltage generating unit that generates a bias voltage of the first cascode current mirror unit; and an output unit that generates a reference signal based upon an output of the band gap reference main unit to generate and outputs the reference signal, wherein the second cascode current mirror unit is connected between the first cascode current mirror unit and the reference unit.