An instrument amplifier is an improved version of a differential amplifier, featuring input buffers that eliminate the need for input impedance matching, making the amplifier suitable for use in electronic instruments such as measurement devices. Commonly used methods mainly involve amplifying微弱 signals at the front end and suppressing the input of interference signals.
Taking the JY Electronics AD620 as an example, the AD620 instrument amplifier has the following characteristics: a maximum operating current of 1.3 mA, an input offset voltage of 5 μV, a maximum input offset voltage drift of 1 μV/°C, a common-mode rejection ratio (CMRR) of 93 dB, adjustable voltage gain, good circuit adaptability, and low noise.
The JY Electronics AD620 is also a three-stage amplification circuit with a high common-mode rejection ratio, excellent temperature stability, a wide amplification bandwidth, and low noise. It also offers the benefits of high precision and ease of use, making it very popular. This makes it a high-performance, low-cost instrument amplifier circuit chip that has become the industry standard, and it is also widely used in the consumer electronics industry.
Three Application Cases of JY Electronics AD620
- 01、Portable ECG Monitor
In the design of ECG monitoring circuits, the signal source impedance is very high, and the portability of the device requires the design to use amplifiers with low power consumption and low supply voltage. The AD620 is the best choice for such devices. The figure shows the application of AD620 in ECG monitoring circuits. Moreover, the low voltage noise of AD620 improves the dynamic range, giving the monitoring circuit better performance. To maintain the stability of the driving loop in the figure, the value of capacitor C1 should be chosen appropriately.
- 02、Pressure Sensor
The AD620 is particularly suitable for the circuit design of pressure sensors with high resistance values and low supply voltages. The small size and low power consumption of AD620 are important factors in the application of pressure sensors. The figure shows a pressure sensor bridge with a resistance of 3kΩ and a +5V power supply. In such a circuit, the bridge power consumption is only 1.7mA. The AD620 and AD705 buffer voltage drivers adjust the signal, making the total power supply current only 3.8mA, and the noise and drift generated by this circuit are also very low.
- 03、Precision Voltage-Current Converter
The AD620 combined with an operational amplifier can be designed into a precision voltage-current converter. By buffering the reference end of AD620 with AD705, excellent common-mode rejection is maintained. The Vx of AD620 is converted into current through resistor R1. This current is as small as the input bias current of the operational amplifier AD705 and then flows out to the load.
The JY Electronics AD620 is a low-cost, high-precision instrument amplifier that only requires one external resistor to set the gain, with a gain range of 1 to 10,000. In addition, the AD620 is available in 8-pin SOIC and DIP packages, which are smaller than discrete circuit designs and have lower power consumption (the maximum power supply current is only 1.3 mA), making it suitable for battery-powered and portable (or remote) applications.
