Power Amplifier Bias Circuit for Temperature-Stable Gain
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Solution Overview
Problem
Existing power amplifier circuits fail to adequately compensate for changes in gain due to temperature fluctuations, particularly at increased temperatures, leading to decreased performance.
Innovation Solution
Incorporation of a constant-voltage generation circuit and diode-connected transistors to stabilize the base current of the power transistor, ensuring the gain remains consistent across varying temperatures through thermal coupling and controlled voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pair of diode-connected transistors are used to bias the driver transistor, then the base current of the power transistor remains substantially constant and stable at the operating point, but the gain of the power transistor is insufficiently compensated when temperature increases
Solution Approach 1:
A constant voltage generation circuit is introduced as an intermediary component to provide a stable reference voltage to the base of the power transistor. This mediator circuit compensates for temperature-induced gain changes by maintaining a consistent voltage level that counteracts the thermal effects on the transistor's amplification capability.
Solution Approach 2:
The invention changes the voltage parameter applied to the base of the power transistor by introducing a constant voltage generation circuit. This voltage parameter is specifically designed to remain stable across temperature variations, thereby compensating for the temperature-dependent gain changes in the power transistor while maintaining reliable base current operation.
2Stability of the object's composition
If the base current is stabilized using diode-connected transistors, then the operating point remains stable, but the gain decreases at increased temperatures
Solution Approach 1:
The constant voltage generation circuit serves as a mediator between the stable operating point requirement and the temperature-compensated gain requirement. It provides a reference voltage that maintains operating point stability while simultaneously compensating for temperature-induced gain variations in the power amplifier.
Solution Approach 2:
By changing the voltage parameter at the base of the power transistor through the constant voltage generation circuit, the invention achieves both stable operating point composition and temperature-insensitive gain performance. The constant voltage parameter counteracts thermal effects without disrupting the established operating point.
Data Source
AI summary
A power amplifier circuit includes an amplifier that operates on power supplied from a first terminal; a first transistor having a collector or a drain, an emitter or a source, and a base or a gate; a first diode having an anode and a cathode, the anode being connected to the control terminal; a second diode having an anode and a cathode, the anode being connected to the cathode of the first diode, the cathode being connected to ground; a second transistor having a collector or a drain, a base or a gate, and an emitter or a source; and a constant-voltage generation circuit that supplies a constant voltage to the base or the gate of the second transistor.