Current Output Circuit Stabilizes Drain Voltage
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Solution Overview
Problem
Existing current output circuits in power amplification modules are unable to maintain a stable output current due to variations in power supply voltage, affecting the stability of the bias current supplied.
Innovation Solution
A current output circuit comprising a first and second FET, each with a power supply voltage at the source and a common gate voltage, controlled by first and second control circuits to maintain equal drain voltages and target current levels, ensuring stability regardless of power supply voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a current mirror circuit is used to generate output current, then the circuit structure is simple, but the output current varies with power supply voltage variations
Solution Approach 1:
The patent employs feedback mechanisms where the control circuit continuously monitors the drain voltages of both FETs and adjusts the gate voltage accordingly. This feedback loop ensures that the drain voltages remain equal, compensating for power supply variations and maintaining stable output current while preserving the current mirror structure's simplicity.
Solution Approach 2:
The patent dynamically adjusts the gate voltage parameter of the FETs based on detected drain voltage differences. By changing this electrical parameter in response to power supply variations, the system maintains equal drain voltages and stable current ratio without fundamentally altering the circuit topology.
2Reliability
If the size of FET is increased to improve current stability, then the output current stability improves, but the device area increases
Solution Approach 1:
The feedback control mechanism allows the use of smaller FETs by actively compensating for voltage variations through real-time gate voltage adjustment. The control circuit detects drain voltage differences and modifies gate voltages to maintain equal drain voltages, achieving current stability without requiring larger device dimensions.
Solution Approach 2:
By dynamically changing the gate voltage parameter, the system achieves current stability control without relying on increased FET size. This parameter-based control approach allows smaller FETs to deliver stable current output, reducing the required device area while maintaining reliability.
Data Source
AI summary
Provided is a current output circuit that includes: a first FET that has a power supply voltage supplied to a source thereof, that has a first voltage supplied to a gate thereof and that outputs a first current from a drain thereof; a second FET that has the power supply voltage supplied to a source thereof, that has the first voltage supplied to a gate thereof and that outputs an output current from a drain thereof; a first control circuit that controls the first voltage such that the first current comes to be at a target level; and a second control circuit that performs control such that a drain voltage of the first FET and a drain voltage of the second FET are made equal to each other.