Amplifier Current Mirror Feedback for Stable Gain Modes
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Solution Overview
Problem
Current current mirror circuits, particularly those using MOSFETs, face challenges in maintaining ideal current-voltage relationships due to channel length modulation, leading to instability and difficulty in adjusting current values.
Innovation Solution
The proposed amplification circuit incorporates a first and second variable current source, along with operational amplifiers and mirror-branch circuits, to generate reference currents that are synchronously related to the operation current, allowing for multiple gain modes and precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If MOSFET is operated in saturation region to increase drain bias voltage, then amplification capability is improved, but channel length modulation effect causes current instability
Solution Approach 1:
The patent employs feedback mechanisms where the operational amplifier continuously monitors the output current and adjusts the gate voltage of the MOSFET to compensate for channel length modulation effects. This feedback loop maintains a stable relationship between reference current and output current despite variations in drain bias voltage, resolving the contradiction between amplification capability and current stability.
Solution Approach 2:
The patent dynamically adjusts the gate-source voltage parameter to compensate for changes in drain-source voltage. By changing the control voltage parameter in response to operating conditions, the circuit maintains ideal current relationships even when the MOSFET operates in the saturation region with varying channel length, thus preserving both amplification capability and current stability.
2Device complexity
If fixed current value is used in amplification circuit, then circuit structure is simplified, but controllability of current amplification is reduced
Solution Approach 1:
The patent transforms the fixed current source into a dynamic, adjustable current source. The operational amplifier and control circuitry enable the reference current to be varied while maintaining the simplified current mirror structure. This dynamic adjustment capability allows the circuit to adapt to different gain requirements without complicating the fundamental current mirror architecture, resolving the contradiction between structural simplicity and current controllability.
Solution Approach 2:
The patent designs the amplification circuit to serve multiple functions: it acts as both a current amplifier and a gain-controlled variable amplifier. The same basic circuit structure supports different gain modes by adjusting the reference current, making the circuit universally applicable across different operating conditions while maintaining structural simplicity. This multi-functionality resolves the contradiction by enabling adaptability without proportional increase in complexity.
Data Source
AI summary
An amplification circuit includes an amplifier, a first mirror-branch circuit, a second mirror-branch circuit, a first variable current source, a second variable current source, and an operation amplifier. The amplifier can receive an operation current and an input signal, and output the amplified input signal. The first mirror-branch circuit and the second mirror-branch circuit are coupled to the amplifier. The first variable current source is coupled to the first mirror-branch circuit and provides a first reference current. The second variable current source is coupled to the second mirror-branch circuit and provides a second reference current. The operation amplifier is coupled to the first mirror-branch circuit, the second mirror-branch circuit and the amplifier. The first reference current and the second reference current are related to the operation current.