Temperature-Coefficient Bias Circuit for Stable Amplifier Gain
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Solution Overview
Problem
Existing amplifier bias circuits struggle to maintain constant gain over a broad temperature range, especially when using non-like-kind devices or in environments with rapid temperature fluctuations.
Innovation Solution
A controllable temperature coefficient bias (CTCB) circuit is introduced, which provides independent control over the current level at a reference temperature and the slope of the temperature coefficient, allowing for precise adjustment of the bias current to maintain constant gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional bias circuit is used, then the circuit is simple, but the amplifier gain cannot be maintained constant over a broad temperature range
Solution Approach 1:
The bias circuit is segmented into multiple independent controllable current sources, each responsible for different aspects of the bias current (magnitude control and temperature coefficient control). This segmentation allows independent adjustment of each function, achieving constant gain over temperature while maintaining reasonable circuit complexity.
Solution Approach 2:
The bias circuit transitions from a static design to a dynamic one with independent control over bias current magnitude and temperature coefficient. This dynamic control enables the circuit to adapt to temperature changes and maintain constant amplifier gain across a broad temperature range.
2Reliability
If like-kind devices are used for temperature compensation, then the temperature coefficient matching is accurate, but the circuit cannot operate when like-kind devices are unavailable
Solution Approach 1:
The invention changes the approach from matching device characteristics (like-kind devices) to directly controlling temperature coefficient parameters through independent current sources. This parameter-based control method achieves accurate temperature compensation without requiring specific device matching, thereby improving both reliability and adaptability.
Solution Approach 2:
The patent introduces controllable current sources as intermediaries between the temperature sensor and the amplifier bias. These current sources act as mediators that convert temperature information into appropriate bias current adjustments, eliminating the need for direct device matching while maintaining compensation accuracy.
3Stability of the object's composition
If the bias current is increased to maintain gain at high temperatures, then the gain stability improves, but the power consumption increases
Solution Approach 1:
The bias circuit dynamically adjusts the temperature coefficient of the bias current based on actual temperature conditions rather than using a fixed high current. This dynamic adjustment maintains gain stability while minimizing power consumption by applying only the necessary current correction at each temperature point.
Solution Approach 2:
The invention changes the bias current parameters (magnitude and temperature coefficient) based on temperature feedback rather than using a fixed high current. This parameter optimization achieves gain stability while reducing unnecessary power consumption that would occur with a constantly high bias current.
Data Source
AI summary
A controllable temperature coefficient bias (CTCB) circuit is disclosed. The CTCB circuit can provide a bias to an amplifier. The CTCB circuit includes a variable with temperature (VWT) circuit having a reference circuit and a control circuit. The control circuit has a control output, a first current control element and a second current control element. Each current control element has a “controllable” resistance. One of the two current control elements may have a relatively high temperature coefficient and another a relatively low temperature coefficient. A controllable resistance of one of the current control elements increases when the controllable resistance of the other current control element decreases. However, the “total resistance” of the current control circuit remains constant with a constant temperature. The VWT circuit has an output with a temperature coefficient that is determined by the relative amount of current that flows through each current control element of the control circuit. A Current Digital to Analog Converter (IDAC) scales the output of the VWT and provides the scaled output to an amplifier bias input.