Feature

●Power supply: 5V-24V can be, but depends on how much the baby with the voltage output (if the customer requires output 5V voltage, then the AD62X series of chips is about ± 3.8V power supply, the regulator chip itself has a pressure difference, so it is recommended that the voltage is higher than 12V single Power supply is better)
●Bandwidth: AD620/623 is lower than 50KHz at high gain and greater than 1MHz at low gain Input signal type: single-ended signal or differential signal
●The maximum magnification: more than 2000 times (actual measurement), due to the gain assembly resulting in greater fluctuations in the waveform band, it is recommended to use high-gain multi-stage amplification
●Saturation output amplitude: AC peak 10Vpp (±5Vpp)
●This module can be enlarged 1000 times, the circuit layout is regular, MINI, design layout and wiring are reasonable


Description

Introduction

AD620 is a low-cost, high-precision instrumentation amplifier. It only needs an external resistor to set the gain. The gain range is 1 to 10,000. Very suitable for battery-powered and portable (or remote) applications. AD620 has high accuracy, low offset voltage and low offset drift characteristics. It is an ideal choice for precision data acquisition systems such as electronic scales and sensor interfaces.

It also has low noise, low input bias current and low power consumption characteristics, making it very suitable for medical applications such as ECG and non-invasive blood pressure monitors.

Fundamental

The instrumentation amplifier is an improvement of the differential amplifier. It has an input buffer and does not require input impedance matching, making the amplifier suitable for measurement and electronic instruments. Features include very low DC offset, low drift, low noise, very high open loop gain, very large common-mode rejection ratio, and high input impedance. Instrumentation amplifiers are used in circuits that require very high accuracy and stability.

3D-PCB

AD620 Differential AmplifierAD620 Differential Amplifier

Schematic & 3D-PCB

The power supply range of AD620 is larger than that of AD623. In order to be compatible with AD623 chip design, a positive and negative 5V power supply is adopted. Step down from a single power supply and then convert to a negative power supply

Chip selection

AD620 and AD623 chips, a low-cost, high-precision instrumentation amplifier, only need an external resistor to set the gain, the gain range is 1 to 10000 (ad623 is 1000) times. The two chips are interoperable on the pins, but the calculation formula of gain is different. The gain of AD620 is G =49.4 kΩ/R G + 1, and the gain of AD623 is G =100 kΩ/R G + 1. The gain bandwidth product parameters are also similar, all within 1M, which are basically used for low-frequency signals. For instrumentation amplifiers with higher gain bandwidth, AD8421 can be used, but note that the chip pins are not compatible.

AD620 Diagram

AD620 Voltage Amplifier Module AD620 Voltage Amplifier Module

Specific explanation

  1. In single-ended mode, plug the jumper cap on the P1 jumper terminal, select 0 ohm for the resistance of R3, IN- is directly grounded, and the signal is input from IN+. Generally, single-ended input can use SMA socket or IN+ and GND input signal .
  2. In single-ended mode, R6 is the bias adjustment potentiometer of IN+, and also the zero-adjusting resistance when single-ended is used. R7, R8 choose 10K to limit the over-adjustment of the bias.
  3. In the differential input mode, the potentiometer and the jumper cap of P1 need to be removed. The resistors R3, R5 and C1, C3, and C5 at the input constitute a low-pass filter. The module does not actually have welding capacitors, and users can weld them according to their needs.
  4. The magnification configuration of single-ended and differential modes, RG is equal to the parallel of R2 and R1, the module in actual use defaults to welding R2 fixed resistance. If you need slip adjustment, you can remove the R2 resistor and solder the R1 potentiometer. AD620:G=49.4K/RG+1 AD623: G=100K/RG+1.
  5. The REF pin of the chip is the output voltage reference. Since the chip is powered by a positive and negative power supply, connect the REF pin to GND here, and the output is centered on 0. If you need to adjust the output reference, you can connect a variable voltage here.
  6. The D2 diode is the input anti-reverse connection. The LM317 step-down chip has two points to note. One is that D1 is the protection diode of LM317, and the other is that the filter capacitor of C25 is needed to reduce the ripple. The general value is 0.1uF to 1uF .
  7. ICL7660 charge pump chip is used to turn negative power supply, which can turn positive pressure into negative pressure, but there will be a certain voltage drop. It can still be used where the supply voltage is not high. C9 is an energy storage capacitor, generally above 10uF. It is particularly important to note that the polarity and capacitance of C13 generally use an electrolytic capacitor above 10uF.

Parameter

Module model AD620
Module type Weak signal amplifier
Input signal form Single-ended or differential, Jumper cap can switch input form
Input voltage range 100uV-1Vpp
Module supply voltage DC6. 5V-26V
Module power supply current 20mA
Output voltage range ±5V (MAX)
Output current 10mA (max)
Module gain range 1-1000 times, The default is 10 times
Bias voltage adjustment range ± 2V (MAX)
Input offset voltage 200uV (MAX)
Input offset drift 2uV/°C1 (MAX)
Input bias current 125nA (MAX)
Common mode rejection ratio 90dB (MIN, G = 10)
Input voltage noise 35nV Hz (1KHz)
Module weight 10g

Module protection: Have, Anti-reverse diode protection

Module weight: 16g

Module specifications: 50*50* 7mm Length * width * height, PCB size

Module heating: No heat sink, The linear voltage stabilized signal of the module with large input voltage may heat up

Module heating factor: The input and output voltage difference is too large or the module is damaged

Module working temperature: -40C~+75℃ Industrial Grade

Module features: Output power LED indication, output 5V linear power

Scope of application: Load cell, data acquisition front end, etc.

Interface diagram

AD620 Low Power Instrumentation Amplifier AD620 Low Power Instrumentation Amplifier

Precautions for module use

  1. The power supply of the module is a single power supply, and the voltage cannot exceed 26V.
  2. Since the module is a high-precision device, in order to avoid unnecessary interference, it is recommended to use a linear power supply.
  3. For the output signal, it is recommended to use the SMA to BNC line to input and output signals. Use an oscilloscope to observe the effect. Poor contact or poor quality wires may cause signal attenuation or excessive noise.

FAQ

Q1: How to adjust zero when the module is single-ended input?

A: The module defaults to single-ended input. After IN+ is grounded with a resistance, you can adjust R6 to zero, or input signal to adjust R6 to zero.

Q2: The module is single-ended by default. What should I do if I need to input a differential signal?

A: When you need to input a differential signal, first remove the jumper cap, then remove the R6 potentiometer, the differential input bias cannot be adjusted, and then use IN+ and IN- to input.

Q3: After welding the gain potentiometer, what is the situation when there is no response when adjusting the gain of the potentiometer?om

A: The module has a default magnification. The soldered potentiometer and the default resistance R2 are connected in parallel. First of all, the potentiometer is multi-turn and needs to be adjusted a few more turns, or the adjustment is more sensitive after removing the R2 resistance.