Switchable Bias Circuit in Power Amplifiers for Low-Power Gain Stability
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Solution Overview
Problem
Existing power amplification circuits face increased current consumption at low output power, leading to degradation of gain characteristics, particularly due to the discharging speed of transistors being higher than charging speed when output power is low.
Innovation Solution
A power amplification circuit with a bias circuit that includes a first transistor and a control circuit with a resistance element and a switch element, where the switch is activated in high power mode and deactivated in low power mode to manage bias current efficiently, reducing current consumption without degrading gain characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If transistor Q2 is used to discharge the amplification transistor at low output power, then the discharging speed is sufficient, but current consumption increases due to current flowing through Q2
Solution Approach 1:
The patent applies dynamics by making the bias circuit configuration changeable based on operating conditions. The switch element dynamically reconfigures the bias circuit between two modes: at low output power, the first transistor is disconnected to reduce current consumption; at high output power, the first transistor is connected to provide sufficient discharge current. This dynamic adaptation resolves the contradiction between maintaining fast discharging speed and reducing current consumption.
Solution Approach 2:
The patent changes the electrical parameters of the bias circuit based on power mode. By controlling the switch element to connect or disconnect the first transistor, the circuit parameters (current flow paths, resistance values) are adjusted according to the output power level. This parameter change allows the circuit to optimize between discharge speed and current consumption for different operating conditions.
2Reliability
If transistor Q2 is used to discharge the amplification transistor, then linearity is improved at high output power, but current consumption increases at low output power
Solution Approach 1:
The bias circuit dynamically adapts its configuration based on power mode requirements. At high output power, the first transistor remains connected to maintain linearity through sufficient discharge capability. At low output power, the switch disconnects the first transistor to eliminate unnecessary current flow. This dynamic behavior resolves the contradiction between maintaining linearity and reducing current consumption.
Solution Approach 2:
The circuit parameters are changed based on operating conditions. The switch element controls whether the first transistor is included in the bias circuit, thereby changing the current flow characteristics. This parameter change allows the circuit to optimize linearity at high power while minimizing current consumption at low power.
Data Source
AI summary
A power amplification circuit includes: a first amplification transistor, a first signal being input to a base or gate thereof and a second signal obtained by amplifying the first signal being output from a collector or drain thereof; and a first bias circuit that supplies a first bias current to the base or gate of the first amplification transistor. The first bias circuit includes a first transistor that outputs the first bias current from an emitter or source thereof, and a first control circuit that controls an electrical connection between the emitter or source of the first transistor and ground. The first control circuit includes a first resistance element and a first switch element, which are connected in series with each other. The first switch element is switched on in the case of a first power mode and is switched off in the case of a second power mode.