Performance Analyses of the Newly Developed Operational Amplifier aRD820

TL;DR

This paper introduces the aRD820, a low-power, cost-effective operational amplifier designed as an alternative to the AD820, with optimized specifications for high-sensitivity analog applications.

Contribution

The paper details the design modifications and testing of the aRD820, demonstrating it meets or exceeds key performance metrics of the AD820 while being suitable for cost-effective production.

Findings

Achieves low voltage noise (< 4 uV peak-to-peak)

Demonstrates ultra-low input bias current (< 15 pA)

Provides comparable gain and offset stability to AD820

Abstract

Operational amplifiers are critical components in modern analog electronics, widely used across applications such as signal conditioning, instrumentation, voltage regulation, and analog-to-digital conversion. This paper presents the design, development, and evaluation of the aRD820, a low-power, rail-to-rail operational amplifier, as a cost-effective alternative to the industry-standard AD820. The aRD820 is optimized for operation on a single supply voltage ranging from 5 to 30 V or a dual supply of +-2.5 V to +-15 V. Key design objectives included achieving low voltage noise (< 4 uV peak-to-peak from 0.1 to 10 Hz), ultra-low input bias current (< 15 pA), and a low offset voltage (< 500 uV), making it suitable for high-sensitivity applications. In adapting the AD820 design, RD Alfa Microelectronics addressed specific production constraints by modifying key circuit elements to meet the specifics of available production facilities. The modified input stage reduced noise by incorporating source followers, enhancing the allowable input signal range. Adjustments to the second and output stages improved phase stability and gain characteristics. Extensive testing of the aRD820 in both wafer form and TO-5 packaged chips confirmed that the amplifier meets or exceeds planned specifications. Comparative results demonstrate that the aRD820 provides open-loop gain, offset voltage stability, and output saturation voltages comparable to those of the AD820. Noise measurements yielded values within the planned range, with an input noise density of approximately 13.5 - 18.1 nV/Sqrt(Hz), suitable for applications requiring precision signal processing. This paper provides a comprehensive overview of the design modifications and test results, establishing the aRD820 as a viable alternative to existing op-amps in similar applications.