Offers both excellent common-mode noise rejection and versatile, compact size for car audio external input blocks

September 5, 2006

Stereo Audio Isolation Amplifier NJM2794

September 5, 2006 - New Japan Radio Co., Ltd. is pleased to announce the NJM2794, a stereo audio isolation amplifier, ideal for rejection of common-mode noise that is caused by GND (ground) potential difference between electronic devices when in-car electronics devices such as car audio are connected.

These days, car audio systems are not only music playback devices such as built-in CD/MD tuners. They are also entertainment systems, incorporating external input devices such as CD changers and DVD or other mobile digital audio players. As a result, the demand for high-quality sound and image technology is increasing, making demand for the removal of common-mode noise - the noise that occurs between the main unit and external input devices - increase as well. To meet this demand, we developed the NJM2794, a stereo isolation amp with a high common-mode rejection ratio.

The NJM2794 is an IC that employs 2 isolation amps configured by 4 operational amplifiers, a resistance for a difference amplifier, and a reference voltage circuit. It features over 50dB high CMRR (Common Mode Rejection Ratio) that indicates the ratio of common-mode rejection, which can be achieved by high precision resistances. To achieve over 50dB CMRR with a conventional discreet circuit, you would need high precision resistances as well as fine design and fine selection of components, but with the NJM2794, you can reduce engineers' strain.

Also, by incorporating 2 independent isolation amps with independent circuits(this is called "dual-mono configuration") the NJM2794 offers excellent channel separation (CS=-110dB), and features improved noise characteristics (1.3µVrms typ.) because all employed amps have a reduced noise level. Moreover, the NJM2794 is housed in a small TVSP10 packaging (3.1×4.0×1mm) to save space. That gives the NJM2794 a simple structure with high-quality performance, making it ideal for car audio external input blocks, which require compact devices with a high common-mode rejection ratio. This product is also efficient when common-mode noise rejection is required between printed circuit boards or units in digital devices, giving it numerous applications.

Compared with conventional products, the NJM2794 features;
  1. High common-mode rejection ratio (CMRR=50dB min.). If configured with discreet circuit, the relative precision of resistance has to be 0.3% or less.
  2. Excellent audio performance
    • Channel separation  CS = -110dB typ.
    • Low noise  Vn = 1.3µVrms
    • Wide dynamic range  Vim > 2Vrms (CD standard output value)
  3. Housed in small, space-saving TVSP10 (3.1×4×1mm).
Product Name Function Applications Packaging
NJM2794 2-circuit audio isolation amplifier Car audio etc. TVSP10,SSOP14
[ Features and Characteristics ]
· Operating voltage 4.3 to 13.0V
· Maximum output voltage 2Vrms min. @THD = 0.1%
· High common-mode rejection ratio CMRR = 50dB min.
· Low output noise voltage 1.3µVrms typ.
· Bipolar technology
· Packaging TVSP10 (3.1×4.0×1mm, 0.5mm pitch),
SSOP14 (5.0×6.4×1.15mm,0.65mm pitch)
[ Schedule ]
  Engineering Samples (ES):From August 2006
  Mass Production (MP):From September 2006
A detailed spec is here