Composite HDD Preamplifier Output Stage With Dynamic Current Control
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Solution Overview
Problem
Conventional output stages in hard disk drive preamplifiers for mobile and portable devices suffer from high power dissipation, limiting battery life due to constant current sourcing, which is inefficient and does not meet the desired total harmonic distortion (THD) requirements.
Innovation Solution
The output stage incorporates a composite amplifier with PMOSFETS and bipolar junction transistors, where current sources are controlled by differential input signals, reducing power consumption while maintaining compliance with the 0.5% THD requirement, using impedance matching elements to optimize signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current sourcing is used in the output stage, then the circuit operates reliably, but power dissipation increases
Solution Approach 1:
The patent implements dynamic current control in the output stage by replacing constant current sources with voltage-controlled current sources. The bias voltages Vb1 and Vb2 dynamically adjust the current through transistors Q3-Q6 based on the differential input signal, allowing the circuit to operate reliably only when needed rather than continuously sourcing current.
Solution Approach 2:
The patent changes the operating parameters of the output stage by introducing variable bias voltages that modulate the current flow. The differential input signal (Vin+ - Vin-) directly controls the current distribution through the transistor network, enabling the circuit to adapt its power consumption to the signal requirements.
2Stability of the object's composition
If constant current sourcing is used in the output stage, then the circuit maintains stable operation, but power consumption increases
Solution Approach 1:
The patent implements dynamic current control in the output stage by replacing constant current sources with voltage-controlled current sources. The bias voltages Vb1 and Vb2 dynamically adjust the current through transistors Q3-Q6 based on the differential input signal, allowing the circuit to operate reliably only when needed rather than continuously sourcing current.
Solution Approach 2:
The patent employs feedback mechanisms where the differential input signal directly controls the bias voltages applied to the current-controlled transistors. This feedback loop ensures that current is sourced only in response to actual input signals, maintaining stability while reducing unnecessary power consumption during idle periods.
3Use of energy by stationary object
If current supply is reduced to save power, then power efficiency improves, but signal quality may deteriorate
Solution Approach 1:
The patent implements dynamic current control in the output stage by replacing constant current sources with voltage-controlled current sources. The bias voltages Vb1 and Vb2 dynamically adjust the current through transistors Q3-Q6 based on the differential input signal, allowing the circuit to operate reliably only when needed rather than continuously sourcing current.
Solution Approach 2:
The patent changes the operating parameters of the output stage by introducing variable bias voltages that modulate the current flow. The differential input signal (Vin+ - Vin-) directly controls the current distribution through the transistor network, enabling the circuit to adapt its power consumption to the signal requirements.
Data Source
AI summary
An apparatus for supplying a load current. The apparatus comprises a first differential amplifier producing a differential output signal and an output buffer comprising a first and a second parallel emitter follower transistors each producing a current responsive to the differential output signal. A second differential amplifier responsive to the differential output signal controls current mirror masters that in turn control current source mirrors. Current supplied by each of the current sources mirrors in cooperation with the current produced by each of the first and second transistors produce the load current.