Jiangsu Runshi: RS620 Adjustable-Gain Instrumentation Amplifier
Instrumentation amplifiers are high-tech, high-barrier products in the analog signal-chain domain, characterized by stringent performance specifications and heavy reliance on advanced manufacturing processes. For a long time, they have been sourced exclusively from European and American suppliers. Leading European and American manufacturers, through continuous optimization and technological upgrades tailored to the application needs of industries such as industrial automation, power systems, healthcare, and motion control, have progressively developed and refined a comprehensive portfolio of models that covers low-, mid-, and high-end applications. Due to technical barriers—particularly constraints in manufacturing processes—domestic-process-based instrumentation amplifier products for civilian applications have long been nonexistent.
To address process-related limitations, Runshi Technology has pioneered the launch of fixed-gain instrumentation amplifiers—RS631B and RS633—designed using domestic manufacturing processes. These devices hardwire the gain value into the circuit design, thereby eliminating the need for thick-film resistor-based gain-setting. Compared with conventional instrumentation amplifiers that rely on external resistors to set gain, this fixed-gain approach not only meets the urgent demand for domestic substitution in certain applications but also simplifies the design by removing the requirement for a high-precision resistor. However, it cannot accommodate application scenarios that require flexible, in-line gain adjustment.
With the continuous optimization and maturation of domestic thick-film resistor technology, a solid foundation has been laid for the design of instrumentation amplifiers with adjustable gain, leading to the development of the all-domestic RS620 adjustable-gain instrumentation amplifier.
The RS620 is primarily benchmarked against the AD620 in terms of its specifications, with parameter performance optimized to the greatest extent possible based on process characteristics. Its key parameter specifications are as follows:
Adjustable gain, supporting gain settings from 1 to 1000.
Gain error: 0.1%, maximum 0.3% (G=10)
Gain temperature coefficient: 15 ppm/°C, maximum 50 ppm/°C
-3 dB unity-gain bandwidth: 1.8 MHz
Slew Rate: 1.8 V/μs
Low input offset voltage: typical value 10 μV, maximum 50 μV
Low input bias current: maximum 2 nA at room temperature
Ultra-low noise: 0.28 μVpp (G ≥ 100)
Common-mode input voltage range: (V−) +0.1 V to (V+) −1.5 V
High common-mode rejection ratio (CMRR) of 138 dB (G = 100);
High power-supply ripple rejection ratio (PSRR) of 127 dB (G = 100);
Low power consumption: 2.2 mA;
Wide operating voltage range: 4.5 V to 36 V (±2.25 V to ±18 V)
Extends the industrial-grade operating temperature range to -40°C to 125°C.
Internal architecture of the RS620: 
As shown in the figure above, the circuit design must ensure that the six internal resistors provide sufficiently precise values to meet the performance specifications of the programmable-gain instrumentation amplifier.
Comparison of Key Specifications Between the RS620 and Competing Products:
Package and pinout definitions for the RS620:
Package: The RS620 uses an SOP8 package, with package dimensions and pin configuration fully compatible with the AD620.
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