Same-Polarity Current Mirror Amplifier for Symmetric Class-A Output
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Solution Overview
Problem
Existing amplification circuits with current-current conversion circuits face challenges in achieving high linearity and low idle current when used in totem-pole output stages, leading to asymmetrical output circuits and degraded characteristics.
Innovation Solution
The amplification circuit incorporates a current-current conversion circuit with transistors of the same polarity, utilizing a diode-connected configuration and current mirror circuits to maintain symmetry and ensure translinear operation, thereby achieving high linearity and low idle current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current-current conversion circuit with complementary transistors is used in a traditional push-pull output stage, then the circuit can provide symmetrical output currents, but the circuit complexity increases and the characteristics degrade when applied to totem-pole output stages
Solution Approach 1:
The patent applies asymmetry by using transistors of the same polarity (all NPN or all PNP) instead of complementary transistors, and introduces asymmetrical current mirror circuits to compensate for the inherent asymmetry in totem-pole configurations. This allows the circuit to achieve symmetrical output characteristics while being optimized for totem-pole output stages.
Solution Approach 2:
The patent changes the fundamental parameter of transistor polarity configuration from complementary (NPN-PNP) to same-polarity (all NPN or all PNP), and adjusts current mirror ratios to achieve symmetrical output characteristics suitable for totem-pole output stages.
2Use of energy by moving object
If the collector current of transistors is reduced to achieve low idle current, then power consumption decreases, but the transistors may be cut off and the circuit cannot maintain class-A operation
Solution Approach 1:
The patent uses feedback mechanisms through current mirror circuits to maintain appropriate current levels in the transistors, ensuring they remain in the active region even at low idle current settings, thereby preserving class-A operation while minimizing power consumption.
Solution Approach 2:
The patent optimizes the current mirror ratios and biasing parameters to maintain transistor currents above cutoff thresholds while achieving low overall idle current, enabling class-A operation with minimal power consumption.
3Reliability
If different current mirror circuits are added to NPN and PNP transistor sides to achieve symmetrical output, then output symmetry is improved, but the device complexity and number of components increase
Solution Approach 1:
The patent uses universal same-polarity transistors for all output devices, allowing a single current mirror circuit design to be applied symmetrically to both sides of the totem-pole output stage, reducing component variety and simplifying the overall circuit architecture.
Solution Approach 2:
The patent changes the transistor polarity parameter to be uniform across all output devices, which simplifies the current mirror circuit design and reduces the number of different circuit configurations needed while maintaining output symmetry.
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 enables a same-polarity SEPP amplifier with low idle current and class-A operation, maintaining high linearity and symmetry, capable of driving devices with varying load impedances from 600 Ω to several ohms.
Implementation Method 1
The amplification circuit incorporates a current-current conversion circuit with transistors of the same polarity, utilizing a diode-connected configuration and current mirror circuits to maintain symmetry and ensure translinear operation
Implementation Method 2
the current-current conversion circuit has four transistors that constitute a translinear circuit by using their PN junctions
Data Source
Figure 1~2
Figure 3(a)~3(d)
Figure 4
AI summary
A current-current conversion circuit of an amplification circuit includes transistors of the same polarity. A current-current conversion circuit (100) has a first transistor (Q1), a diode-connected second transistor (Q2) that has the same polarity as the first transistor (Q1), a diode-connected third transistor (Q3) that is connected in series to the first transistor (Q1), and that has the same polarity as the first transistor (Q1), a diode-connected fourth transistor (Q4) that is connected in series to the second transistor (Q2), and that has the same polarity as the first transistor (Q1), and a constant current source (101) that is connected in series to the second (Q2) and fourth (Q4) transistors. An input signal (Ix) is given to the common connection node of the first (Q1) and third (Q3) transistors. A current generation circuit (200) supplies first and second anti-phase currents that are proportional to currents which flow through the first transistor (Q1) and the third transistor (Q3), respectively.