NJM2149D

Overview

The NJM2149D is a low voltage audio power amplifier designed for telephone applications, utilizing bipolar technology. It operates within a supply voltage range of +2V to +6V and delivers an output power exceeding 250mW at V+=6V with a 32Ω load. The typical operating current is 2.2mA at V+=3V, reducing to 0.1µA in power down mode. The device features differential outputs eliminating external coupling capacitors, adjustable closed-loop gain via two resistors, and a CD pin for powering down with input muting.

Feature Summary

• Eliminates the need for external coupling capacitors through differential output configuration.
• Provides a chip disable control (CD) pin that powers down the IC while muting the input signal.
• Offers improved thermal noise reduction in switching power down mode compared to previous models.

Applications

• Portable telephones
• Wireless telephones
• Button telephones

Procurement Notes

Verify the specific package type required, as the NJM2149 series includes multiple variants such as DIP8, DMP8, SSOP8, VSP8, and TVSP8. Confirm that the D suffix corresponds to the desired physical footprint before ordering. Ensure application circuits include appropriate decoupling capacitors on the power supply lines to optimize the supply voltage rejection ratio and stability during operation.

Selection Notes

Select this component for single-channel mono audio amplification where low voltage operation is critical. The differential output architecture simplifies board layout by removing large coupling capacitors. Consider the available gain range of 0-43dB and the ability to drive loads between 8Ω and 200Ω when designing the amplifier stage for specific speaker impedances.

Part Context

The NJM2149D belongs to the NJM2149 family of low voltage audio power amplifiers manufactured by Nisshinbo Micro Devices. This series is engineered specifically for portable communication devices requiring efficient power management. The D suffix indicates the DIP8 package variant, distinguishing it from surface mount options like the M or V series within the same functional family.

Replacement Considerations

The datasheet notes that the NJM2149 improves upon the NJM2135 regarding thermal noise and high-band noise reduction. Designers transitioning from the NJM2135 should verify pin compatibility and circuit requirements, as the NJM2149 offers enhanced performance in power down modes without requiring changes to the fundamental differential output design.

FAQ

How does the CD pin function?

The CD pin controls the power state. Applying a high level (≥2.0V) activates the IC, while applying a low level (≤0.8V) puts the IC into standby mode with muted input.

Are external coupling capacitors required?

No, external coupling capacitors are not required because the NJM2149 utilizes differential outputs.