By Chau Tran, product application engineer, Linear and Precision Technology Group, Analog Devices
Many applications require a gain block, either to amplify a weak signal or to attenuate a large one to match the full-scale input range of an ADC. Unfortunately, typical gain blocks use discrete amplifiers and external resistors, which brings disadvantages, such as low accuracy and drift limitations. For example, with standard 1%, 100ppm/°C gain-setting resistors, the initial gain error to 2% can vary by up to 200ppm/°C.
Generally, precision resistors can be used for precise gain setting, but they are expensive and occupy a lot of space. Also, the gain can vary with temperature since each resistor drifts differently. Hence, there’s a demand for a monolithic amplifier that can provide amplification or attenuation without performance loss.
The IC block diagram configurations shown in Figures 1 and 2 are smaller and offer improved performance at lower cost. This integrated approach is the smallest available for this function, and the circuits require no external components.