Power Amplifier Bias Circuit With Stable Current Mirror Drive
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Solution Overview
Problem
The performance of power amplifiers in wireless transceivers is adversely affected by variations in operating temperature and voltage supply due to fluctuations in bias voltage or current.
Innovation Solution
A power amplifier circuit incorporating a current generator and current mirror driver, which generates a stable current independent of temperature and voltage supply variations, and a bandgap circuit that provides a reference voltage insensitive to these changes, ensuring consistent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional power amplifier circuit is used, then the circuit can amplify signals, but the bias voltage or current varies with operating temperature and voltage supply changes, adversely affecting performance
Solution Approach 1:
The patent uses a current generator circuit that generates a reference current independent of voltage supply variations, and a bandgap circuit that produces a temperature-compensated reference voltage. These circuits change the operating parameters (current and voltage references) to remain stable across temperature and supply variations, directly resolving the bias instability problem
Solution Approach 2:
The patent implements feedback mechanisms where the generated reference current and voltage are fed back to control the bias conditions of the power amplifier. The current mirror driver copies the reference current to bias nodes, and the bandgap circuit provides temperature-compensated voltage feedback, ensuring the bias points remain stable despite external condition changes
2Adaptability or versatility
If the power amplifier operates across a wide temperature range, then the amplifier can function in various environments, but the bias voltage or current varies significantly, degrading performance
Solution Approach 1:
The bandgap circuit specifically addresses temperature variations by generating a reference voltage that compensates for temperature effects. The current generator maintains constant reference current across temperature ranges, allowing the power amplifier to operate reliably from -40°C to +85°C with less than 1.5% variation in bias conditions
Solution Approach 2:
The temperature-compensated reference voltage from the bandgap circuit is fed back through the current mirror driver to continuously adjust and maintain stable bias conditions across the full operating temperature range, ensuring performance reliability in varying environmental conditions
3Adaptability or versatility
If the voltage supply varies, then the power amplifier can tolerate supply fluctuations, but the bias voltage or current changes, affecting amplifier performance
Solution Approach 1:
The current generator circuit is designed to produce a reference current that is independent of voltage supply variations. By changing the reference current parameter to be supply-voltage insensitive, the circuit maintains stable bias conditions even when the power supply voltage fluctuates, directly resolving the bias current stability issue
Solution Approach 2:
The stable reference current from the current generator is fed back through the current mirror driver to the bias nodes, creating a feedback mechanism that maintains constant bias current regardless of voltage supply changes, ensuring the amplifier operates correctly under varying supply conditions
Data Source
AI summary
A power amplifier circuit includes a current generator and a current mirror driver. The current generator has a first input connected to a first voltage supply and an output configured to generate a first current. The current generator includes a first transistor, a second transistor, a first resistor and a second resistor. The first transistor has an emitter connected to ground. The second transistor has a base connected to a base of the first transistor and an emitter connected to ground. The first resistor is connected between the first voltage supply and a collector of the first transistor. The second resistor is connected between the first voltage supply and a collector of the second transistor. The current mirror drive has a first input connected to the output of the current generator to receive the first current and an output configured to generate a second current.