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Op-amps moving toward zero-drift, greater voltage range

Op-amps moving toward zero-drift, greater voltage range
by Majeed Ahmad on 12-27-2014 at 7:00 am

Operational amplifiers, which are among the most widely used analog components found in nearly all types of electronic systems, are migrating toward zero-drift capability and much-greater range of voltages at the supplies and the inputs. Take Linear Technology Corp.’s LTC2057HV, a zero-drift operational amplifier, which features self-calibrating circuitry that provides high DC precision and stability over changes in temperature, time, input range and supply voltage. The LTC2057HV components claim to offer optimal combination of low voltage noise, low current noise and low input bias current, while the zero-drift architecture cancels 1/f noise.

Operational amplifier – commonly known as op-amp – is one of the basic building blocks of analog electronics for functions such as filters. It’s a linear device that boasts all the properties required for nearly ideal DC amplification and is therefore used extensively in signal conditioning, filtering or to perform mathematical operations such as add, subtract, integration and differentiation. An op-amp is basically a three-terminal device which consists of two high impedance inputs, one called the inverting input, marked with a negative or “minus” sign, ( – ) and the other one called the non-inverting input, marked with a positive or “plus” sign ( + ).

Operational amplifier block diagram

A wider range of supply and input voltages is critical because high supply-voltage amps are powered by systems that connect to power systems, automobiles, or large battery packs. Here, the amplifier’s input may be connected to hundreds of volts, but amplifying signals will still be operating in the microvolt range. On the other hand, high-voltage amplifiers also offer features to improve system performance, cost, and robustness, while easing the complexity of system design. The second key element in the ongoing op-amp evolution is zero-drift – a technique originally developed to address constantly changing temperature as well as drift over time. The zero-drift amplifiers dynamically correct offset voltage as well as reshape noise density.

Linear’s LTC2057HV amplifier offers more than 140dB dynamic range while operating on a 60V (±30V) supply. “This wide dynamic range enables tiny signals to be amplified in the presence of much larger signals without saturating the amplifier or losing precision,” said Brian Black, product marketing manager for signal conditioning products. Here, spurious artifacts normally associated with zero-drift amplifiers are suppressed, further extending the dynamic range, stability and useful signal bandwidth.

For applications requiring supply voltages of up to 36V, a lower supply version of LTC2057 is also available. Both LTC2057 and LTC2057HV components – operating over a -40°C to 125°C temperature range – claim to offer low voltage noise, low current noise and low input bias current, while the zero-drift architecture cancels 1/f noise. The input common-mode range includes the negative rail and the output swings rail-to-rail, which makes the LTC2057 component suitable for single- and dual-supply industrial, instrumentation and automotive applications.

The LTC2057 part is available in 3mm x 3mm DFN, MSOP-8 and SOIC-8 packages, as well as an MSOP-10 package with a pin-out that enables a guard ring to be easily routed around the input to preserve the high precision and low noise performance at high source impedance.

Linear’s 60V zero-drift op-amp

High-speed op-amps

Exar Corp., another supplier of analog and mixed-signal chips, has recently launched the XR805x family of high-speed operational amplifiers for applications such as video distribution and surveillance systems. These operational amplifiers are widely used in a vast array of consumer, industrial, and scientific devices.

Exar claims that its operational amplifiers will lower the overall system power consumption and provide higher precision for improved performance. “The XR805x family offers customers an opportunity to make their designs more power efficient and at the same time, improve performance,” said Dale Wedel, Exar’s vice president of High Performance Analog product line. “These pin-for-pin drop-in replacements allow customers to lower power consumption in existing platforms and offer performance enhancements that enable next generation designs.”

The XR805x family of devices is targeted at applications including professional and IPC cameras, active filter circuits, coaxial cable drivers, and electronic white boards. The amplifiers can drive four video loads and operate from a wide supply voltage range to accommodate general-purpose, high-speed applications where dual supplies of up to +/- 6V or single supplies from +2.7V to +12V are required.

Amplifiers often pick up a small signal in a hostile environment and then ride on top of a larger signal. These highly versatile components are the unsung heroes in most of the electronic systems. Op-amps are an increasingly important part of the amplifier recipe, and they are likely to play a crucial part in the future for their role in a diverse range of applications.

Majeed Ahmad is the author of Smartphone, Nokia’s Smartphone Problem, Mobile Commerce 2.0and Essential 4G Guide.He has been writing for technology and trade media for more than 19 years.

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