Bipolar Bandgap Reference Circuit With Base Current Compensation
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Solution Overview
Problem
Conventional bandgap reference voltage generator circuits suffer from flicker noise introduced by MOSFETs, which is a concern for noise-sensitive applications like analog-to-digital converters, and existing solutions like the chopper technique complicate circuitry and require a stable clock source.
Innovation Solution
A bandgap reference voltage generator circuit using only bipolar transistors, incorporating a transconductance amplifier circuit with a differential input to receive base current and a compensation current sink circuit to address base current effects, along with a current buffer circuit to maintain voltage stability and linear operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MOSFETs are used in the current mirroring circuit, then the circuit can be implemented with standard semiconductor devices, but flicker noise is introduced which degrades the reference voltage quality
Solution Approach 1:
The patent changes the device type parameter from MOSFET to bipolar transistor in the current mirroring circuit. This parameter change eliminates flicker noise while maintaining circuit functionality, as bipolar transistors do not exhibit the 1/f noise characteristic of MOSFETs.
Solution Approach 2:
The patent creates a compensation copy of the base current effect by introducing additional bipolar transistors that replicate the base current characteristics. This copy is then used to cancel out the harmful base current effects in the main circuit through differential operation.
2Object-affected harmful factors
If bipolar transistors are used in the current mirroring circuit, then flicker noise is eliminated, but base current effects introduce errors in the reference voltage
Solution Approach 1:
The patent implements a feedback mechanism where the base current effects are detected and compensated through additional bipolar transistors configured to sense and counteract the base current errors, thereby maintaining reference voltage accuracy.
Solution Approach 2:
The patent introduces intermediate bipolar transistors that act as mediators to handle the base current effects. These transistors are specifically configured to absorb or compensate for base current errors, preventing them from affecting the reference voltage output.
3Object-affected harmful factors
If chopper technique is used to reduce flicker noise, then noise performance is improved, but circuit complexity increases and external clock source is required
Solution Approach 1:
The patent extracts the noise generation mechanism at its source by eliminating MOSFETs from the critical signal path. Instead of applying a noise reduction technique like chopping, the design removes the flicker noise source entirely, avoiding the complexity of additional noise mitigation circuitry.
Solution Approach 2:
The patent employs bipolar transistors that inherently provide stable operation without requiring external control signals or clock sources. The circuit serves itself by using the natural characteristics of bipolar transistors to maintain stability, eliminating the need for external clocking infrastructure.
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 solution effectively reduces flicker noise by using bipolar transistors and a compensation current sink circuit, ensuring a stable reference voltage without the need for complex chopper techniques or external clock sources, thereby improving noise immunity in sensitive circuits.
Implementation Method 1
a bandgap reference voltage generator circuit formed using only bipolar transistors... configured to compensate for bipolar base current effects
Data Source
AI summary
A bandgap voltage generator circuit is formed using only bipolar transistors. The bandgap voltage generator circuit includes an output node at which a bandgap reference voltage is generated. A transconductance amplifier circuit in a current control feedback loop has a differential input which receives a base current. A compensation current sink circuit operates to sink a compensation current from the output node corresponding to the base current received at the differential input of the transconductance amplifier.