LMC6442 Op Amp

National Semiconductor Corporation announces availability of a dual micropower rail-to-rail output single supply op amp with new lows in power current consumption - just 0.95 microamp typical supply current per amplifier, and a guaranteed supply current of 1.2 microamp per amplifier. The LMC6442 is characterized for 2.2V to 10V operation and is fully guaranteed at 2.2V, 5V and 10V.

On the low side of the supply range, National's newest op amp is ideally suited for single (Li-Ion) or two-cell (Ni-Cad or alkaline) battery-powered systems that require low standby current for long service life. As battery life approaches end-of-charge state, its performance degradation is minimized by the LMC6442's very low input bias current (5fA typical) plus minimal variations in supply current over supply voltage. To facilitate extremely small circuit designs, the LMC6442 is housed in a mini-small outline (MSOP-8) package that is only one-half the size of a standard small outline IC (SOIC).

"This device achieves superior cost performance with a unique combination of features," said Peter Stonard, National's technical marketing manager. "But the real key to its value is its miserly power consumption. At 2.2V, it's one of the lowest power op amps in the world. In passive battery-powered equipment such as smoke and gas detectors, that single feature can more than triple the battery life," he added.

Rail-to-rail output voltage swings are also especially important with the low supply voltages encountered in battery operation. In the LMC6442, the output swings to within 30mV of the supply rail. The input common mode voltage range extends to the negative rail for ease of use in single supply applications or ground sensing. Unity Gain Bandwidth (GBW) is typically 9.5 kHz, making the IC effective in low-frequency applications.

For more information on the LMC6442, visit our World Wide Web site.

Yet again we have another breakthrough in op amps in 1997. With major announcements already from TI, Motorola and ADI this year, one from National should perhaps come as no shock (certainly not to those privy to it through NDA) but the numbers still sound nice. It is not the perfect op amp by any means but for low-frequency applications it is pretty close. The 0.95 mA typical at 2.2 V multiplies out to an astonishingly low 2 mW and the battery life extension that this will create is highly significant. When you add the 5 fA input bias, the design of non-voltage dependent circuitry, especially for sensors will be much easier.

As National rightly assume, the major applications uses for this part will be in the single-battery detectors used for smoke and gas alarms in the domestic marketplace.

I don't however buy this as a true rail-to-rail output device. It is close at "within 30 mV" but it is not even within 1% at 2.2 V. (1% has become my personal definition until the industry can come to some sort of agreement.)

The MSOP package is tiny but the price of the dual at $1.80 in 1000 piece lots is quite high. Most of the other major breakthough announcers of op amps have chosen to launch their products with little price premium, and even in the 8-pin SOIC National have chosen to kep the price up there at $1.75 in 1000 piece lots. The performance is also way up there but there may be some resistance to paying this price. A great product nonetheless.