The ultra low power LT1672, LT1673 and LT1674 are the single, dual and quad members of the industry's only family of high voltage capable, rail-to-rail input and output, precision operational amplifiers that draw just 1.5µA typical and 2µA Max supply current.

Despite drawing less supply current than the self-discharge of most batteries these decompensated (AV>5) amplifiers feature wide gain bandwidth product (12kHz) and lower input voltage noise (0.1Hz to 10Hz noise = 4µVp-p) than amplifiers that draw many times the 1.5µA supply. Unlike other low power op amps the LT1672/73/74 do not stress the supply during start up. The supply current is controlled during power on and is limited to approximately 2µA typ. The higher start-up supply current required by other op amps can quickly exhaust a battery and in the extreme case lead to a power system not starting up at all.

Most competitive low power, rail-to-rail op amps have low maximum supply voltage capability, typically limiting their use to 3V or 5V regulated supplies in relatively benign environments. Not so the LT1672/73/74 family. These rugged op amps feature a wide supply voltage range from 2.2V to 36V and protection against reverse battery connection to 18V, making them suitable for use in even 12V lead acid battery applications. Unique to Linear Technology op amps is the Over-The-Top feature. This allows the inputs to function correctly even when one or both are above the positive supply. Rail-to Rail, Over-The-Top input op amps are ideal for high side current sensing applications and can even be used to allow a low voltage system to sense a higher voltage supply.

The part's ultra low power and rugged design are complemented by other equally impressive amplifier specifications -- namely a maximum input offset voltage of 375µV, low offset voltage drift of just 0.4µV/°C (max 2µV/°C), high open loop gain 215V/mV, CMRR and PSRR of 90dB Min and low input offset and bias current of only 20pA and 250pA respectively.

These op amps are ideal for battery or solar-powered systems and remote instrumentation as well as industrial applications such as 4 to 20mA current-loop transmitters.

"The LT1672, LT1673 and LT1674 are unique amongst the ultra low power op amps. No other family of rail-to-rail amplifiers can match the precision, high voltage capability and rugged design of these op amps,ý says design manager Bill Jett. "This combination of features keeps the errors low regardless of supply, temperature or input signal making them extremely easy to use."

This is a particularly nice combination of features: There is an extremely low supply current, an excellent voltage range for many industrial applications while the amplifier quality is still maintained.

The supply current is 2 µA maximum per amplifier with a supply range from 2.2 to 36 V. The output swing is from about 210 mV (sinking 100 µA) to about 160 mV below the rail (at 5 V) with similar types of numbers under other rail conditions.