Incorporating the industry's best rail-to-rail output, a tiny high output current CMOS operational amplifier from Micrel is easy to use and stable even driving loads with capacitance as high at 6000pF, when operating off a 10V supply. Micrel Semiconductor, designer and manufacturer of the MIC7300 family, is an industry leader in analog and power management integrated circuits.

"CMOS op amps are ideally suited for low-voltage, single-rail applications, but until now they have had relatively low output drive capability and many have been unable to drive even relatively low capacitance loads," said Scott Brown, linear marketing manager. "The MIC7300 can sink and source in excess of 80mA and its stability makes it much easier to use than existing CMOS devices."

The MIC7300 has an input common-mode range that exceeds the supplies, and an output that will swing to within 1mV of the rails when driving a 100k ohm load.

"The MIC7300 offers leading-edge rail-to-rail output performance," said Brown, "We know of no other device capable of swinging as close to the supplies as the MIC7300."

For space-conscious applications, the MIC7300 comes in Micrel's 5-pin IttyBitty SOT23-5 package. For higher power applications, the MIC7300 will soon be available in an MSOP-8 package with a fused leadframe for enhanced thermal dissipation. The MSOP-8 package will enable users to fully exploit the excellent output-drive capability of the MIC7300.

Slew rate of 0.5V/ýs, combined with a gain bandwidth product of 0.5MHz and a supply current of 0.5mA, make the MIC7300 ideal for general purpose signal conditioning and buffering applications. Low input bias current of 1pA and the high output drive capability make the MIC7300 ideal for buffering high-impedance sensors.

One day the industry is going to define rail-to-rail in terms of what percentage of rail voltage the inputs or outputs will swing to. That time is not coming soon, unfortunately, but this Micrel part is the closest I have seen in a "hard-driver" product. I think, in percentage terms, that Motorola's 1-V op amp (the "Vyne" amplifier) gets a little closer. But this MIC7300 has one heck of an output punch and the 80 mA drive with swings to within 1 mV at 10 V is certainly unique and will enable designers make a much more stable amplifier stage without that much care having to be taken. And there is nothing wrong with the price.

I also like the input bias current at 1 pA and the fact that Micrel guarantees performance at 2.2, 3, 5 and 10 V rails.

This is an ideal device in sensor applications where the user wants to provide as much punch as possible from a single stage. In the SOT23-5 this will mean that the amplifier can be right alongside the sensor so reducing interference and noise problems in any number of applications, probably immediately before an ADC. One of the most likely applications for that situation is in handheld, bettery instruments.

The MIC7300 is in production and is priced at $0.75 in 1000-piece lots. As noted, it is in a SOT23-5 with a special leadframe MSOP-8 to be made available in the future. We can probably assume that there will also be multiples available in the future using the same circuitry.