Power (gm


) against aging and TID radiation. Because its dynamic thresholds remain practically unchanged under exposure, the system circumvents the voltage hunting and instability phenomena typical of silicon-regulated loops. This proves that the time-domain response remains predictable and robust throughout the satellite’s operational lifecycle without requiring over-designed loop margins. The typical transfer characteristics (Figure 2) that define the stability of these systems are anchored in the specific behaviour of the pass elements under distinct temperatures and biasing configurations.


Discussion, thermodynamics, and conclusions


Managing continuous linear power dissipation (PD


= (Vin - Vout ) . Iout ) in space Figure 1. Total Ionizing Dose (TID) performance displaying the high stability of Vgs(th)


Conversely, the lower asymptotic boundary of the theoretical dropout voltage (Vdo(min)


up to 500 kRad for GaN technology.


control loop based on a minimalist parallel resistor-capacitor network (Rcomp


, Ccomp ) is initially modelled by


summing the ohmic losses across the partially enhanced semiconductor channel and the voltage drop across the series- connected current sense resistor (Rcs Vdo(min)


): ≅ Iout . (Rds(on_sat) + Rcs )


However, physical characterization on the test bench reveals a distinct deviation from the simplified static mathematical model. To reconcile this discrepancy for high-precision aerospace applications, the proposed analytical model formally incorporates the distributed ohmic resistance of the PCB copper traces (Rtrace


)


and the coupling effects of the gate parasitic inductance (Lgate


Lgate . (dIgate


= Iout /dt)


. (Rds(on_sat) + Rcs ), which alters the


dynamic operating point at the saturation boundary of the device: Vdo(real)


+ Rtrace ) +


This analytical method successfully isolates geometric parasitic variables from the semiconductor’s intrinsic variations, yielding a consolidated transfer equation for the regulated output voltage (Vout


)


governed by the feedback resistor network ratio (Ro2


/Ro1 = ((Ro2


reference (VREF Vout


) and the internal bandgap = 2.5 V):


/Ro1 ) + 1) . VREF - (Iout . Rcs )


Results and transient response To validate the analytical model without the interference of complex compensation networks that could mask the intrinsic dynamics of the eGaN HEMT, an analogue


www.cieonline.co.uk )


was implemented. System verification was conducted utilizing time-domain load transient simulations, complemented by empirical bench testing under severe load current variations (dI/dt).


The experimental results demonstrate that linear architectures utilizing eGaN pass elements exhibit rapid recovery windows and remain entirely free of parasitic oscillations across their full operating boundaries. In high-current configurations subjected to a dynamic step from 0.1 A to 5 A, the analogue control


loop dampens the transition within a


recovery time () of approximately 50 µs, restricting the peak voltage deviation amplitude to a maximum of ~160 mV. Conversely, in configurations optimized for precision low-magnitude loads (current steps from 0.05 A to 0.5 A), the reduced internal parasitic capacitance profile of the semiconductor decreases the recovery time to ~40 µs and limits the maximum transient deviation to a nominal 110 mV. This accelerated transient response confirms the stability of the control loop, which is directly linked to the structural consistency of the GaN transconductance


environments presents a critical challenge due to the lack of convective cooling. To experimentally validate the thermodynamic behaviour of the control loop without resorting to bulky mechanical heatsinks, the EPC7C023 evaluation platform (optimized for high-current regimes up to 5 A) and the EPC7C024 platform (designed for precision analogue loads up to 0.5 A), both developed by EPC Space, were utilized as test vehicles. These platforms demonstrated the feasibility of lateral heat routing into internal PCB copper planes using planar aluminium nitride (AlN) helper elements. This dynamic thermal decoupling is essential for high-density aerospace electronics, as it prevents localized hot spots from shifting the operational thresholds of adjacent low-voltage reference circuits.


In conclusion, the structural validation of eGaN HEMTs within LDO linear regulator topologies bridges a critical technological gap in spacecraft power distribution infrastructure. The results confirm that Gallium Nitride is no longer restricted to high-frequency switching converters but can operate as a reliable, stable pass element for continuous linear DC regulation. By eliminating heavy physical radiation shielding and completely mitigating end- of-life parameter drift induced by TID, this architecture allows aerospace engineers to consolidate component procurement under a single, highly versatile semiconductor platform, paving the way for lighter, more efficient, and highly ruggedized power electronics optimized for long-duration orbital missions.


Figure 2. Typical transconductance curve (Id high-current linear regulation architectures.


vs.Vgs ) for the EPC7019G (40 V/90 A) pass element utilized in https://epc.space/ Components in Electronics September 2026 35


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