The first integrated-circuit op-amp (the µA 709) came out in the mid-1960s. Considering the vast chasm that separates the capabilities of modern op-amps from those of early models, it is somewhat surprising that we are still using the same word to refer to all these devices. And after all these years, new op-amps are still appearing—the fact is, parts always have some characteristic or specification that can be at least a little better.
Power consumption (more specifically, lower power consumption) is a major development area for new ICs, and op-amps are no exception. High-frequency capabilities are also a priority, but of course there are trade-offs involved when extending an op-amp’s usable bandwidth, so we should always consider slower parts for low-frequency applications.
And of course there is input offset voltage. The offset voltage—actually, the offset voltage multiplied by the noninverting gain—is a direct contribution to the total error of your amplifier circuit, and in high-precision applications it can really ruin your day if you’re not careful.
The LTC6260 is a quad op-amp marketed as a high-performance yet low-power replacement for existing devices. It has the usual capabilities we expect from modern op-amps: low offset voltage, rail-to-rail input and output, low-voltage operation, high power supply rejection ratio (PSRR). However, Linear Tech believes that this amplifier surpasses what is typically available when you combine its various high-performance features with its low current consumption.
Image courtesy of Linear Technology
One interesting characteristic of this op-amp is its tolerance for significant capacitance on the output line: “drives all capacitive loads,” according to the datasheet. As you probably know, capacitive loads traditionally are a problem for op-amps because they can lead to instability. But apparently you won’t have to worry too much about this if you choose the right op-amp; Linear Tech’s “special compensation technique” allows the amplifier to maintain stability at unity gain even when driving high-capacitance loads.
In this age of gigahertz processors and corresponding gigahertz lifestyles, it’s nice to see a new product that is conspicuous for its low-frequency characteristics. The MAX40006 has a gain-bandwidth product of only 300 kHz, but Maxim is quick to remind us that (as indicated above) lower speed allows for other advantages: the part description refers to a “maximized ratio of gain bandwidth (GBW) to supply current.”
Like the LTC6260, the MAX40006 offers low supply voltage, rail-to-rail input and output, etc., but the current consumption is significantly lower:
Image courtesy of Maxim Integrated (PDF)
And if you really need to conserve power, you can use the part’s shutdown mode to reduce the supply current to 0.1 µA. The MAX40006 seems like a promising option for battery-powered applications that are dealing with lower-frequency analog signals such as temperature measurements or audio.
The TSZ182 from STMicro is faster (GBW = 3 MHz) than the two previous parts, but it also has much higher current consumption:
Image courtesy of STMicroelectronics
However, my guess is that power consumption wasn’t the design priority here—offset voltage was. The LTC6260 has a maximum VOS of 400 µV; for the MAX40006, it’s 1000 µV. But the TSZ182? A mere 45 µV (max) over the entire –40°C to +125°C temperature range, and 3.5 µV typical at 25°C.
Image courtesy of STMicroelectronics
If you have an application in which power consumption is much less important than ensuring very-high-precision analog signal processing, you should take a look at the TSZ182.
Are you particularly impressed with any recently released op-amps? Let us know in the comments.