The HJMAG803A high-temperature, three-axis, high-precision weak magnetic field measurement module carried aboard the satellite.

In modern electronic devices, operational amplifiers are an indispensable component. Particularly in the design of domestically produced op‑amp circuits, selecting appropriate components and optimizing the circuit architecture have become focal points for many engineers. Today, we will delve into the key principles and techniques of designing domestic op‑amp circuits, helping you elevate your circuit‑design expertise. 1. Understand the Basic Characteristics of Operational Amplifiers First and foremost, when designing a domestic op‑amp circuit, it is essential to grasp the amplifier’s fundamental characteristics. The core performance of an op‑amp hinges on parameters such as gain, input impedance, and output impedance. Gain determines the signal‑amplification capability; input impedance affects the source‑load interaction; and output impedance influences the signal‑transmission efficiency. Only by thoroughly understanding these basic traits can we proceed with more effective circuit design. 2. Choose the Right Domestic Operational Amplifier While the market offers a wide array of domestically manufactured op‑amps, not every model is suitable for your specific project. When making your selection, consider several critical factors: bandwidth, power consumption, operating temperature range, and cost. For instance, if your application involves high‑frequency signal processing, bandwidth becomes the primary consideration. Conversely, for projects with stringent low‑power requirements, prioritize low‑power consumption.

At 18:51 on October 14, 2021, two “Made in Shenzhen” microsatellites—the Commercial Meteorological Constellation Test Satellite and the Orbital Atmospheric Density Test Satellite—were successfully launched from the Taiyuan Satellite Launch Center aboard a Long March‑2D carrier rocket. Building on thorough preliminary testing and evaluation, the mission carried our company’s HJMAG803A high‑temperature three‑axis weak magnetic field measurement module. This not only bolstered both organizations’ confidence in deepening their collaboration but also demonstrated that Hangjing’s years of dedicated effort have stood up to real‑world application. We will, as always, uphold the spirit of craftsmanship, continuously enhance the consistency and reliability of our products, and realize our aspiration to contribute to the nation through advanced microelectronics by delivering high‑performance products and services that consistently exceed customer expectations.

 

 

Figure 1: Physical image of the satellite

 

 

Figure 2: On-site Assembly Diagram

 

HJMAG803A is a high-temperature, three-axis, high-precision weak magnetic field measurement module. The circuit comprises an oscillation source, an acceleration network, a drive network, a voltage‑doubling network, an amplification network, a synchronous demodulation network, an integration network, a feedback network, a bias circuit, and a temperature‑measurement circuit. It employs a magnetoresistive sensor circuit to measure the ambient geomagnetic field, enabling mutual conversion between geomagnetic signals and voltage signals. The module can operate at temperatures up to 175°C.

 

Figure 3: Block Diagram of the Principle

 

 

Figure 4: Physical Product

 

Figure 5: Module Packaging Forms

 

 

 

This weak‑magnetic‑field measurement module is primarily used to determine the satellite’s angular orientation relative to Earth’s magnetic field (along the Ox, Oy, and Oz axes), providing critical data for attitude control. Compared with conventional fluxgate sensors, it offers advantages such as low power consumption, high reliability, excellent stability, and a compact form factor. The incorporation of an analog PID loop further minimizes secondary nonlinearities and long‑term drift. This series of weak‑magnetic‑field modules has found widespread application in downhole measurement while drilling (MWD), gamma‑ray logging, pitch‑angle measurement, inertial navigation, and reference‑free rotational speed sensing. Several high‑precision, in‑house‑developed models have already been deployed across diverse sectors, including oilfield operations and satellite technology. The product lineup includes the HJMAG803, HJMAG804, HJMAG805A, and others.