AD623BR

AD623BR Application Field and Working Principle

The AD623BR is a universal, low power, low-noise, high-linearity, low-cost logarithmic amplifier suitable for a wide range of applications. It is part of the family of Analog Devices’ logarithmic amplifiers, which includes the AD723, AD7311 and AD731. The AD623BR is more commonly used in industries such as manufacturing, healthcare, automotive and military.

Overview

The AD623BR is a high-performance logarithmic amplifier, capable of providing linearity to better than 0.01% over its full operating temperature range, with a typical input-referred noise of 4 μV RMS. A single-supply operation of ±3 to ±18 VDC is possible which makes the AD623BR ideal for operation in the ±75 mV to ±30 VDC range, which gives it a wide range of applications.

The AD623BR has a low-power operating range from 2 to 10 mA and is designed for single-supply operation with both positive and negative input/output polarities. Its low power consumption makes it suitable for use in battery-operated devices. It also has an input/output common mode range that is extended to exceed the power supply range by 1.5 V.

Application Fields

The AD623BR logarithmic amplifier can be used in a variety of applications, the most common being in audio and RF amplification, medical equipment, manufacturing, healthcare, automotive and military equipment. Due to its accuracy and low power consumption, it is suitable for use in a variety of industrial, scientific and medical applications. For example, it can be used in audio and RF communications, medical equipment, process control, electronic test and measurement, laboratory experiments, industrial instrumentation, and more.

In audio applications, the AD623BR can be used to measure the distortion of an audio signal up to 64 logarithmic decibels. This can help to detect disturbances in audio signals that may be due to electrical interference or changes in audio frequency. The logarithmic response of the AD623BR allows it to measure the dynamic range of an audio signal and detect any overloading of the system. The AD623BR can also be used in radio communications to measure the strength of a radio signal, allowing it to be used in the design of radio links.

In medical applications, the AD623BR can be used to detect changes in the temperature of a patient’s body or to measure blood oxygen levels. It can also be used to measure dynamic range in EEGs as well as measure the heart rate and rhythm of a patient. The AD623BR can also be used for process control and safety applications, such as detecting explosive conditions in a gas detector.

A variety of applications in the military can also benefit from the AD623BR, including detecting the presence of an enemy aircraft in a radar system, and measuring the position of an airborne object. It can also be used in guidance systems and navigation controls.

Working Principle

The AD623BR is a current-mode logarithmic amplifier. It provides a accurate logarithmic output, by utilizing a single charge-balancing current source. This current source creates a voltage on the feedback resistor that is directly proportional to the input signal. At the same time, charge on the output capacitor is proportional to the input current, which then delivers the logarithmic output voltage.

The AD623BR also uses a differential, current output stage to control the output voltage, as well as two post-amplifier, low-noise current sources. These low-noise current sources act as an internal noise filter, minimising noise and ensuring accurate measurements. The AD623BR also features an adjustable offset voltage, allowing for further versatility in applications.

Conclusion

The AD623BR is a versatile and reliable logarithmic amplifier from Analog Devices, designed for a wide range of applications. It is capable of providing excellent linearity and low-noise performance, and can operate from a single supply with both positive and negative input/output polarities. Its wide variety of applications make it suitable for use in audio, RF communications and medical equipment, as well as process control and safety applications, and more.