Reference Buffer Circuit Charge Pump Voltage Shifting
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Solution Overview
Problem
Conventional reference buffer circuits face challenges in providing a wide dynamic range of reference voltages due to physical limitations, particularly in analog to digital converters, where the low output voltage is bounded by the gate-to-source voltage of PMOS transistors, limiting the driving capability under low power supply conditions.
Innovation Solution
The introduction of charge pumps in the tracking loops of operational amplifiers allows for dynamic adjustment of driving voltages, enabling higher high output voltages and lower low output voltages without turning off transistors, thereby expanding the dynamic range by shifting the voltage levels through capacitors and switches, and optional low-pass filtering to prevent voltage spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional reference buffer circuit structure is used, then circuit simplicity is maintained, but dynamic range of reference voltages is limited due to transistor gate-to-source voltage constraints
Solution Approach 1:
A charge pump circuit is introduced as an intermediary component between the operational amplifier and the transistor gate. The charge pump shifts the voltage level dynamically, allowing the transistor gate-to-source voltage to remain within safe operating limits while the actual reference voltage output can extend beyond traditional bounds. This mediator enables extended dynamic range without directly compromising transistor operation.
Solution Approach 2:
The invention dynamically changes the voltage level parameter at the transistor gate through the charge pump mechanism. By shifting the gate voltage level in response to control signals, the circuit can achieve higher high output voltages and lower low output voltages while maintaining proper transistor biasing conditions. This parameter transformation resolves the contradiction between extended range and circuit simplicity.
2Use of energy by moving object
If supply power is reduced, then power consumption is lowered, but driving capability of reference buffer circuit deteriorates
Solution Approach 1:
The charge pump circuit introduces dynamic voltage level shifting capability that allows the reference buffer to maintain strong driving capability across a wider voltage range. By dynamically adjusting the gate voltage level rather than relying on static headroom, the circuit achieves robust performance at lower supply voltages. The dynamic operation of the charge pump enables the circuit to adapt its driving capability to match the reduced supply power conditions.
3Adaptability or versatility
If low output voltage is reduced to expand dynamic range, then voltage range is increased, but transistor operation becomes unstable due to gate-to-source voltage constraints
Solution Approach 1:
The charge pump serves as a voltage level mediator that decouples the relationship between output voltage level and transistor gate-to-source voltage. It shifts the gate voltage level dynamically, ensuring that even when the output voltage approaches extreme values, the transistor maintains stable operation with appropriate gate-to-source voltage. This intermediary function protects transistor stability while enabling expanded voltage range.
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 enhances the dynamic range of reference voltages, allowing for robust operation under lower power supply conditions without increasing static current consumption, and can be applied to various reference generator circuits.
Implementation Method 1
a first charge pump coupled to an output end of the first operational amplifier, for shifting a level of the first tracking voltage to generate the first driving voltage
Implementation Method 2
a first capacitor C1 having a first end P1 and a second end P2, and a second capacitor C2 having a positive end Q1 and a negative end Q2
Implementation Method 3
optional low-pass filtering to prevent voltage spikes
Data Source
AI summary
A reference buffer circuit is provided, comprising a reference buffering stage and a driving stage. The buffering stage provides a first driving voltage based on a first input voltage. The driving stage is driven by the first driving voltage to output a first output voltage. In the buffering stage, a first operational amplifier has a first input end for receiving the first input voltage, a second input end, and an output end for outputting a first tracking voltage. A first level shifter is coupled to the output end of the first operational amplifier, shifting a level of the first tracking voltage to generate the first driving voltage. A first buffering transistor has a drain coupled to a first supply voltage, a source connected to the second input end of the first operational amplifier, and a gate coupled to the first charge pump for receiving the first driving voltage.