Low-Noise Current Source With Shunt Regulator And Parallel Modules
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Solution Overview
Problem
Current current sources for driving quantum cascade lasers (QCLs) face challenges in providing low noise output current with high compliance voltage and long-term stability, especially when delivering high currents and voltages, due to limitations in operational amplifier noise and sensing resistor thermal noise, which deteriorate at high output voltage conditions.
Innovation Solution
A low-noise current source architecture with parallel current generator modules, an active feedback loop, and a shunt-type regulator supplies the error amplifier stage independently of the DC supply, reducing noise contributions and allowing for high compliance voltages and stable current delivery through a modular, scalable design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current source architecture with operational amplifier and sensing resistor is used, then current regulation function is achieved, but noise increases and stability deteriorates at high output voltage conditions
Solution Approach 1:
The current source is divided into multiple independent current generator modules operating in parallel, each contributing to the total output current. This segmentation distributes the noise burden and improves overall stability, as each module can be optimized independently and their noise contributions partially cancel out due to statistical independence.
Solution Approach 2:
A shunt-type regulator is introduced as an intermediary component to supply the error amplifier stage independently from the DC supply. This intermediary power supply isolates the sensitive error amplifier from noise and voltage fluctuations in the main power supply, significantly improving long-term stability and reducing noise at high output voltage conditions.
2Adaptability or versatility
If high compliance voltage is provided to enable high current and voltage applications, then application versatility is improved, but noise contributions from operational amplifier and sensing resistor increase
Solution Approach 1:
The shunt-type regulator acts as an intermediary power supply for the error amplifier, decoupling it from the main DC supply. This allows the error amplifier to maintain low noise performance even when the output stage operates at high compliance voltages, as the intermediary supply provides clean, stable power independent of output conditions.
Solution Approach 2:
By segmenting the current source into parallel modules, each module operates at a fraction of the total current, reducing the thermal noise from sensing resistors and operational amplifiers. The modular architecture allows high compliance voltage to be achieved across the parallel combination without proportionally increasing noise in each individual module.
3Reliability
If modular parallel architecture with shunt-type regulator is implemented, then noise is reduced and stability is improved, but device complexity increases
Solution Approach 1:
The current source is segmented into identical, modular current generator units that can be replicated and connected in parallel. This modular approach, while increasing component count, simplifies design verification, manufacturing, and maintenance, as each module is a standardized building block with well-defined interfaces and functions.
Solution Approach 2:
The shunt-type regulator is designed as a universal power supply module that can serve multiple error amplifiers in the parallel architecture. This multi-functional component reduces overall system complexity by providing a standardized power interface that works across all current generator modules, rather than requiring dedicated power circuits for each module.
Data Source
Figure 1(a)~2b
Figure 2a
Figure 3~4
AI summary
Low-noise current source, configured to be supplied by at least one DC main supply (Vss) and to deliver an output current (h), the source comprising one or more current generator modules (G1, G2,... GN) operating in parallel each one of which is configured to deliver a respective output current (I i ), whereby the output current (I L ) of the source is equal to the sum of the output currents (I i ) di said one or more current generator modules (G1, G2,... GN), each current generator module (G1; G2;... GN) comprising a regulator component (Q1), configured to deliver the output current (L) of the current generator module (G1; G2;... GN), a sensing resistor (Rs) connected in series to the regulator component (Ql), and an error amplifier stage (ICl), configured to compare a reference voltage (Vrej) with a voltage drop ( Vs) across the sensing resistor (Rs), whereby the error amplifier stage (IC1) is configured to amplify an error signal equa l to a difference between the between voltage (Vrej) and voltage across the resistor (Rs) di sensing, the error amplifier stage (IC1) being configured to output the amplified error signal that is configured to control the regulator component (Ql), the current source being characterised in that each current generator module (Gi; G2;... GN) further comprises a first shunt type regulator (Z1, l1), configured to be connected to said at least one DC main supply (Vss), that is further configured to generate a dedicated supply voltage supplying the error amplifier stage (IC1), whereby the error amplifier stage (IC1) is configured to be supplied in a floating manner with respect to said at least one DC main supply ( Vss).