====== LamaPLC: CJMCU-8221 Analog Devices Precision instrumentation amplifier module ======
{{ :sensor:cjmcu_8221_1.png?120|CJMCU-8221 Analog Devices Precision instrumentation amplifier module}}
The **CJMCU-8221** is a high-performance, gain-programmable precision instrumentation amplifier module based on the **AD8221AR** chip by Analog Devices. It is specifically designed to amplify small signals in noisy environments with high accuracy.

=== Key Technical Specifications ===
  * **Core Chip:** Analog Devices AD8221.
  * **Programmable Gain:** Set via a single external resistor from 1 to 1000.
  * **Supply Voltage:** Supports single or dual supplies from ±2.3 V to ±18 V.
  * **High CMRR:** Minimum Common-Mode Rejection Ratio (CMRR) of 80 dB to 90 dB (at G=1), enabling rejection of wideband interference and line harmonics.
  * **Low Noise:** Input voltage noise of approximately 8 nV/√Hz at 1 kHz.
  * **Form Factor:** Compact MSOP package on a breakout board for easy prototyping. 

=== CJMCU-8221 Pinout ===
^Pin #^Mnemonic^Description|
|1|-IN|Negative Input Terminal for the differential signal.|
|2|RG|Gain Setting Terminal. Connect one end of the gain resistor here.|
|3|RG|Gain Setting Terminal. Connect the other end of the resistor here.|
|4|+IN|Positive Input Terminal for the differential signal.|
|5|-VS|Negative Power Supply. Connect to negative rail (e.g., -5V) or Ground for a single supply.|
|6|REF|Reference Voltage. Sets the output "zero" level. Typically connected to Ground (GND).|
|7|VOUT|Output Signal. The amplified result of (+IN) - (-IN).|
|8|+VS|Positive Power Supply. Connect to positive rail (e.g., +5V to +18V).|

  * **Dual vs. Single Supply:** While it can operate on a single supply (4.6V to 36V), using a dual supply (±2.3V to ±18V) is recommended to ensure the output can swing fully to zero.
  * **REF Pin:** Do not leave this pin floating. Tie it to GND for a 0V reference or to a specific voltage if you need to level-shift the output.
  * **Decoupling:** Always place bypass capacitors (e.g., 0.1µF) between the supply pins and ground to minimize noise.

=== Gain Calculation === 
The gain (G) of the module is determined by the external resistor (R<sub>G</sub>) connected across the R<sub>G</sub> pins. Use the following formula:

^Target Gain^Resistor (R<sub>G</sub)|
|1|Open (No resistor)|
|10|5.49 kΩ|
|100|499 Ω|	
|1000|49.4 Ω|	

//Many breakout boards come with a pre-soldered 499 Ω resistor, setting the default gain to approximately 100.// 

=== Arduino Code Example ===
<code c>
void setup() {
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(A0);
  // OUT Pin: Connect to an Arduino Analog Input (e.g., A0)
  float voltage = sensorValue * (5.0 / 1023.0); // Convert to voltage
  Serial.println(voltage);
  delay(100);
}
</code>

{{tag>CJMCU-8221 AD8221AR Analog_Devices amplifier sensor}}

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