Current Compensation Circuit for Stable Parasitic BJT Collector Current
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Solution Overview
Problem
Existing semiconductor devices face challenges in maintaining a constant collector current in parasitic bipolar transistors due to variations in current gain, particularly when the current gain is small, leading to fluctuations in base-emitter diode voltage.
Innovation Solution
A current compensation circuit is implemented using a series of transistors and a constant current source to supply a compensated current to the emitter of a parasitic bipolar transistor, ensuring a constant collector current regardless of current gain variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current is supplied to the emitter terminal of a parasitic bipolar transistor, then the collector current becomes constant, but the base current cannot be ignored due to small current gain, causing the collector current to vary
Solution Approach 1:
The patent introduces a compensation circuit as an intermediary between the constant current source and the parasitic bipolar transistor. This compensation circuit measures the base current and generates a compensation current that flows through the base terminal, effectively canceling the base current's effect on the collector current. This mediator approach allows the system to maintain constant collector current despite small current gain values.
Solution Approach 2:
The compensation circuit implements a feedback mechanism by continuously monitoring the base current and adjusting the compensation current accordingly. The circuit uses the base current information to generate an equal and opposite compensation current, creating a closed-loop system that maintains constant collector current. This feedback approach dynamically compensates for variations in current gain.
2Stability of the object's composition
If the emitter current is kept constant in a parasitic bipolar transistor with small current gain, then the collector current varies due to base current branching, leading to voltage variations in the base-emitter diode
Solution Approach 1:
The compensation circuit acts as an intermediary that introduces a compensation current through the base terminal. This compensation current serves as a mediator that counteracts the base current branching effect, allowing the emitter current to remain constant while preventing variations in the base-emitter diode voltage. The compensation current effectively bridges the gap between constant emitter current and stable base-emitter voltage.
3Device complexity
If a simple constant current source is used for the parasitic bipolar transistor, then the circuit complexity is low, but the collector current cannot be kept constant due to base current effects
Solution Approach 1:
The patent segments the current supply function into two distinct parts: a constant current source that provides the main current to the emitter terminal, and a compensation circuit that separately handles the base current compensation. This segmentation allows each component to perform its specific function efficiently - the constant current source maintains overall current stability while the compensation circuit specifically addresses base current effects, achieving reliable collector current constancy without excessive complexity.
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 maintains a stable collector current, reducing variations in base-emitter diode voltage and enhancing the accuracy of temperature sensing applications by stabilizing the emitter current.
Implementation Method 1
a current compensation circuit configured to supply current to an emitter of a first bipolar transistor
Implementation Method 2
a first bipolar transistor including a collector connected to a first power terminal, a base connected to the first power terminal, and the emitter
Data Source
AI summary
A current compensation circuit includes: a second bipolar transistor configured to have a same process variation as the first bipolar transistor; a first transistor including a drain connected to the emitter of the second bipolar transistor; a second transistor including a gate connected to a gate of the first transistor, and a drain connected to its own gate; a third transistor including a drain connected to the emitter of the first bipolar transistor, and a gate connected to the drain of the second transistor and each gate of the first and the second transistors; a constant current source; a fourth transistor including a drain connected to the base of the second bipolar transistor, and a gate connected to its own drain; and a fifth transistor including a drain connected to one end of the constant current source, and a gate connected to the gate of the fourth transistor.