Bias Control Circuit Stabilizes Power Amplifier Voltage

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Solution Overview

Problem

Existing power amplification modules in mobile communication devices face fluctuations in bias voltage or bias current due to manufacturing variations, leading to increased complexity and cost in suppressing these variations.

Innovation Solution

A bias control circuit comprising a reference voltage circuit, a temperature-dependent current generating circuit, a constant current generating circuit, a reference voltage buffer circuit, and a bias generating circuit, which together stabilize the bias voltage or bias current by using a resistor and operational amplifiers to manage temperature-dependent currents and maintain a constant reference voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a current mirror circuit is used to generate constant current from bandgap reference voltage, then the bias voltage or bias current can be generated with temperature dependence, but manufacturing variations in transistor sizes cause variations in the constant current and bias voltage

Engineering Contradiction:

Improvetemperature dependence of bias voltageVSAvoidbias voltage variation

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent introduces a resistor as an intermediary element between the current mirror circuit and the bias generating circuit. This resistor converts the temperature-dependent current into a voltage that can be precisely controlled and buffered, thereby reducing the direct impact of transistor manufacturing variations on the final bias voltage while maintaining the necessary temperature dependence.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a feedback mechanism through the buffer circuit that monitors the voltage across the resistor and adjusts the constant current accordingly. This feedback loop compensates for manufacturing variations in the current mirror circuit, stabilizing the bias voltage despite variations in transistor sizes.

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If the resistance value of a resistor is adjusted to suppress variations in constant current, then the bias voltage stability improves, but the manufacturing process becomes complex and manufacturing cost increases

Engineering Contradiction:

Improvebias voltage stabilityVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The circuit is designed to be self-regulating through the buffer circuit that automatically adjusts the constant current based on the voltage across the resistor. This self-service mechanism eliminates the need for external adjustment of resistor values or complex manufacturing processes, as the circuit automatically compensates for variations during operation.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent changes the operating parameters of the circuit by using a buffer circuit to control the constant current dynamically. Instead of adjusting physical resistor values during manufacturing, the system changes the electrical parameters (current magnitude) to achieve the desired bias voltage stability, thereby simplifying the manufacturing process.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If variations in constant current occur due to transistor manufacturing variations, then the bias voltage or bias current varies, but the power amplification performance deteriorates

Engineering Contradiction:

Improvebias voltage consistencyVSAvoidpower amplification performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The buffer circuit provides real-time feedback control that monitors the voltage across the resistor and adjusts the constant current to maintain stable bias voltage. This feedback mechanism ensures consistent power amplification performance by compensating for current variations before they affect the amplifier output.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The circuit incorporates prior cushioning by pre-compensating for potential current variations through the buffer circuit's regulation mechanism. Before the variations can affect power amplification performance, the buffer circuit has already adjusted the constant current to maintain stable bias conditions, thus cushioning against performance deterioration.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10396718B2Bias control circuit and power amplification module

Publication Date: 2019.08.27 MURATA MFG CO LTD

AI summary

Provided is a bias control circuit that includes: a reference voltage circuit that generates a reference voltage; a resistor; a temperature dependent current generating circuit that generates a temperature dependent current, which changes depending on temperature, on the basis of the reference voltage and that supplies the temperature dependent current to one end of the resistor; a reference voltage buffer circuit that applies the reference voltage to the other end of the resistor; a constant current generating circuit that generates a constant current, which is for driving the reference voltage buffer circuit, on the basis of the reference voltage and that supplies the constant current to the other end of the resistor; and a bias generating circuit that generates a bias voltage or a bias current for a power amplification circuit on the basis of the voltage at the one end of the resistor.