NATIONAL SEMICONDUCTOR INTRODUCES THE FIRST OF A NEW CLASS OF "PRECISION OVER TIME" OPERATIONAL AMPLIFIERS

New Design Self-Corrects Voltage Offset over Time and Temperature While Eliminating 1/f Noise

September 14, 1998 - National Semiconductor Corporation® today announced the LMC2001, the first of a new class of operational amplifiers guaranteeing very high precision over time and temperature over ten years. The LMC2001 is optimized for performance in strain gauges, weight scales, test and instrumentation equipment and climate control systems where precision, low power, and small size are critical.

Today's designers are challenged to increase precision, reduce noise, lower power consumption, save board space and minimize system cost. The LMC2001 addresses these challenges. To increase precision, National's LMC2001 offers precision-over-time technology that ensures 5 microvolt offset error drift over ten years plus the elimination of 1/f noise as a source of signal error. As a result, the LMC2001 offers an ultra-low offset voltage that is entirely stable over time and temperature. The LMC2001 is manufactured on a state-of-the-art submicron BiCMOS process providing a reduction of die size and product cost. The device is the only low cost, high accuracy op amp in a SOT23-5 package.

"Signal accuracy becomes even more critical when op amps are used in low-voltage systems," noted Suneil Parulekar, marketing director for National's amplifier product line. "Digital engineers, often uneasy about the analog side, will welcome National's LMC2001 because it eliminates design complications such as offset error, drift, and 1/f noise. In addition, this op amp can be dropped into existing systems without any modifications.

By definition, 1/f noise increases in amplitude as frequency is reduced. In most applications, this varying signal noise is added or subtracted from the signal to be measured, with a corresponding increase in error. However, 1/f noise error is eliminated in the LMC2001. Additionally, since the voltage and current noise level is low and constant with frequency, accuracy in all DC-coupled applications is greatly improved.

Key Features and Benefits
The LMC2001 offers an unparalleled array of key features and benefits:

• Low input offset voltage (Vos) < 40 microvolt after a mere 15ms of start up time
• Guaranteed maximum Vos drift 5 microvolt / 10yr
• Vos drift over temperature < 0.015 microvolt / degree Celsius
• No 1/f input voltage noise
• Gain Bandwidth Product > 6MHz.

The LMC2001 is designed with special patented techniques, providing all the benefits of traditional chopper-stabilized amplifiers while reducing the effects of the chopper shortcomings. In traditional chopper stabilized amplifiers, the offset voltage is continuously sampled and stored in capacitors in one cycle and nulled in the next cycle. In contrast, the LMC2001 uses a method similar to AM modulation to achieve low offset voltage, and no 1/f noise.

Using a spread spectrum technique, the LMC2001 does not allow the input signal to lock into the internal clock frequency to produce aliasing. This technique, in conjunction with AM modulation, further reduces noise peaks.

In DC performance, the LMC2001 achieves 120dB of CMRR (Common Mode Rejection Ratio), 120dB of PSRR (Power Supply Rejection Ratio) and 137dB of open loop gain at 10k ohm loads. In AC performance, the LMC2001 provides an unmatched 6MHz of gain bandwidth product and 5V/microsecond of slew rate.

Price and Availability
Available now in production quantities, the LMC2001ACM5, in a tiny SOT23-5 package, and LMC2001AIM, in a standard SOIC-8 package, are priced at $1.20 each in 1000-unit quantities.

For more information on the LMC2001, visit our World Wide Web site at http://www.national.com.

National Semiconductor Corporation produces system-on-a-chip silicon solutions for the information highway, based on its leadership in analog and mixed signal technologies. National is headquartered in Santa Clara, California, and focuses on the communications, personal systems and consumer markets. National has annual sales of approximately $2.5 billion and 13,000 employees worldwide. Additional company and product information is available on the World Wide Web at www.national.com.