Diode Feedback LNA Circuit for Temperature-Stable Gain
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Solution Overview
Problem
Existing temperature compensation circuits are not suitable for low noise amplifiers, leading to significant gain fluctuations due to ambient temperature changes, which are not effectively managed by current solutions designed for power amplifiers.
Innovation Solution
A nonlinear feedback circuit incorporating diodes and resistors connected in specific configurations to the enhancement-mode pseudomorphic high electron mobility transistor (pHemt) in low noise amplifiers, combining negative and positive temperature characteristics to stabilize gain and increase P1dB and OIP3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current mirror temperature compensation circuit is used, then temperature compensation is achieved for power amplifiers, but it is not suitable for low noise amplifiers and causes great gain fluctuation
Solution Approach 1:
The patent changes the compensation mechanism from current-based (current mirror) to voltage-based (diode voltage drop). The diode's voltage drop has negative temperature characteristics that compensate for the pHemt's gain variations. By adjusting the number of diodes and resistor values, the compensation amount can be tuned to achieve optimal temperature stability for low noise amplifiers.
Solution Approach 2:
The patent introduces a feedback circuit containing diodes and resistors that form a voltage divider network. This network feeds back a compensated voltage signal to the gate of the pHemt, creating a closed-loop system that automatically adjusts the gate voltage in response to temperature changes, thereby stabilizing the amplifier gain across different temperatures.
2Reliability
If only diode is used for temperature compensation, then negative temperature characteristics are provided, but it is difficult to reach suitable temperature compensation and P1dB is reduced
Solution Approach 1:
The patent creates a composite temperature compensation network by combining diodes (with negative temperature coefficient) and resistors (with positive temperature coefficient). This composite structure allows the positive temperature characteristics of the resistor to counterbalance the negative temperature characteristics of the diode, enabling precise adjustment of the overall temperature compensation effect while maintaining adequate P1dB performance.
3Use of energy by moving object
If voltage divider power supply method is used, then power supply is provided, but gain changes greatly under temperature changes
Solution Approach 1:
The patent introduces a diode-based voltage reference circuit as an intermediary between the power supply and the amplifier gate. Instead of directly applying the voltage divider power supply to the gate, the diode network first compensates for temperature effects and then provides the stabilized gate voltage, thereby decoupling the power supply function from the gain stability requirement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves gain stability and increases OIP3 by effectively compensating for temperature changes, reducing gain fluctuations and enhancing high-order harmonics cancellation, thereby improving the performance of low noise amplifiers across varying temperatures.
Implementation Method 1
the negative temperature characteristics of the diode and the positive temperature characteristics of the first resistor R1 can be combined in a complementary fashion
Implementation Method 2
the negative temperature characteristics of the diode and the positive temperature characteristics of the first resistor R1 can be combined in a complementary fashion
Implementation Method 3
With the first inductor L1, the inductance of L1 can be used to prevent a DC signal from being coupled to the radio frequency
Implementation Method 4
The third resistor R3 can form a high-impedance state to prevent a DC signal from being coupled to the radio frequency end
Data Source
AI summary
The invention discloses a nonlinear feedback circuit, which includes at least one diode. The invention also discloses a low noise amplifier using the nonlinear feedback circuit. In the invention, temperature compensation is performed for the gain change of the low noise amplifier based on the negative temperature characteristics of the diode, thereby achieving gain stability. In addition, the nonlinear characteristics of the diode can also provide high-order harmonics for the low-noise amplifier, and the mutual cancellation and addition of high-order harmonics can increase the OIP3 of the low noise amplifier.