Nisshinbo Launches Dual Operational Amplifiers for High-Quality Audio
The MUSES8921 series of J-FET input dual audio operational amplifiers is built for high-quality sound in audio systems, achieving low noise and distortion within a ±3.5 V to ±17 V operating range.
Nisshinbo Micro Devices has expanded its line of specialized audio components with the introduction of the MUSES8921, a dual operational amplifier. This device is positioned as the new junction field-effect transistor (J-FET) standard model within the company’s established MUSES series. The design is a progression of the former MUSES8920/A model, integrating advanced technical know-how derived from the company’s flagship product.
The MUSES8921 series of J-FET input dual operational amplifiers for use in high-end audio systems. Image used courtesy of Nisshinbo Micro Devices
MUSES8921 Series J-FET Input Dual Operational Amplifier
The core architecture of the MUSES8921 series is a J-FET input stage combined with bipolar technology. The J-FET input stage is critical for high-fidelity signal processing because it offers a low input bias current of 5 pA (typical). This characteristic is particularly advantageous in high-impedance circuits, minimizing voltage drop and loading effects at the input, which is essential for applications like I/V converters and sensor conditioning.
The MUSES8921 series achieves a low noise level of 8.0 nV/√Hz at 1 kHz. This figure is a measure of the input-referred voltage noise density and is a key parameter for preserving the dynamic range and clarity of the input signal, particularly in low-level signal paths like preamplification stages. Simultaneously, the amplifier demonstrates an exceptionally low total harmonic distortion (THD) of 0.0004% at 1 kHz. Low THD is required to ensure the op-amp introduces minimal non-linearity, which translates directly to greater purity in the reproduced audio waveform.
The device is also characterized by a high slew rate of 25 V/μs. Slew rate defines the maximum rate of change of the output voltage. A high value is necessary for accurately reproducing fast-changing or high-frequency transient signals without slew-induced distortion, a phenomenon often associated with intermodulation distortion in high-speed audio signals. The gain bandwidth product is specified at 11 MHz, providing adequate frequency headroom for high-gain applications within the audio band.
The MUSES8921 is built on the earlier MUSES8920/A, part of Nisshinbo’s MUSES standard models. Image used courtesy of Nisshinbo Micro Devices
Design Refinements and System Flexibility
Nisshinbo focused on internal design optimization to enhance transparency and spatial precision in the output signal. This was achieved by a review and optimization of the signal and power paths, as well as the physical placement of circuit elements on the die.
The MUSES8921 is built to offer operational flexibility. It supports a wide dual-rail operating voltage range of ±3.5 V to ±17 V. This range allows the component to be used across diverse platforms, from low-voltage portable devices to higher-voltage professional and home audio equipment.
The device is available in two package options: the EMP-8-AN (a dual-in-line compatible package) and the DFN4035-8-GR (a compact, high-heat-dissipation 4.0 mm × 3.5 mm DFN package). The DFN package is particularly useful for small form-factor designs, such as portable gadgets, while still requiring stable operation at high output power levels due to its thermal efficiency.
The MUSES8921 comes in an EMP-8-AN (left) and DFN4035-8-GR (right) package. Image used courtesy of Nisshinbo Micro Devices
Delivering High-Fidelity Sound
The MUSES8921 dual op-amp leverages a J-FET input and bipolar architecture, resulting in benchmark audio specifications. The device’s low input bias current and design optimizations for signal path integrity make it a versatile component for minimizing non-linearity and preserving signal fidelity. Given its wide supply voltage range and package options, the MUSES8921 is well-suited for integration into high-quality audio preamplifiers, active filters, headphone amplifiers, I/V converters, and general line amplifiers across home, professional, portable, and automotive aftermarket audio systems.
