5 Common Causes of AD620 BRZ Amplifier Saturation and How to Fix Them
The AD620BRZ is a precision instrumentation amplifier widely used for accurate, low-noise signal amplification. However, like any electronic component, it can experience saturation under certain conditions. Saturation occurs when the output voltage reaches its maximum limit and cannot properly represent the input signal, leading to inaccurate measurements. Below are five common causes of AD620BRZ amplifier saturation, along with practical solutions for each:
1. Excessive Input Voltage
Cause: If the input voltage to the amplifier exceeds the operating voltage range, the amplifier can saturate. The AD620BRZ has a limited input voltage range, typically within the supply rails (e.g., ±12V for a ±15V supply).
Solution:
Check the Input Signal: Ensure the input signal stays within the input range specified in the datasheet. For the AD620BRZ, the input should not exceed the Power supply voltage by more than 0.3V. Use Attenuation: If your input signal is too large, use a resistor divider or a variable attenuator to reduce the input voltage. Clamp Input Signals: If necessary, use diodes or clamping circuits to protect the amplifier from large input voltages that could cause saturation.2. Inadequate Power Supply
Cause: Saturation may occur if the AD620BRZ is not powered with the proper supply voltages. The amplifier’s output cannot exceed the supply voltage, and if the supply voltage is too low, the amplifier will reach saturation quickly.
Solution:
Verify Power Supply: Ensure the power supply voltage meets the requirements specified in the datasheet (typically ±12V to ±15V or a single supply of 5V to 12V). Increase Supply Voltage: If using a lower supply voltage, consider increasing it within the allowable limits to provide a wider output swing. Use Dual-Supply if Needed: If you need a larger output swing, consider switching to a dual-supply configuration (e.g., ±15V).3. Incorrect Gain Setting
Cause: The AD620BRZ allows the gain to be set by an external resistor. If the gain is set too high, even a small input signal can drive the output into saturation.
Solution:
Check Gain Resistor Value: Review the resistor used to set the gain (pin 8). If the gain is too high, reduce the value of the resistor to lower the amplification. Calculate Appropriate Gain:Use the formula for setting the gain:
[ G = 1 + \frac{50kΩ}{RG} ] where ( RG ) is the resistor connected between pins 8 and 5. Make sure the calculated gain is appropriate for your signal levels.4. Overdriving the Input Differential
Cause: The input differential voltage (the difference between the non-inverting and inverting inputs) can cause saturation if it’s too large for the amplifier to handle. The AD620BRZ can only amplify a differential voltage within its specified limits.
Solution:
Check the Input Differential: Make sure that the voltage difference between the non-inverting and inverting inputs does not exceed the specified limit in the datasheet (e.g., typically ±40mV for a ±15V supply). Reduce Input Differential Voltage: If the differential input voltage is too large, reduce it by using a voltage divider or attenuating the signal before it reaches the amplifier. Use a Precision Voltage Source: Ensure your signal sources are stable and within the recommended differential voltage range.5. Improper Output Load
Cause: The AD620BRZ may saturate if the load Resistance is too low or too high for the output drive capabilities of the amplifier. For instance, a very low load resistance can draw more current than the amplifier can supply, pushing it into saturation.
Solution:
Check Output Load: Make sure the load resistance connected to the amplifier’s output is within the recommended range (typically 10kΩ or higher). Increase Load Resistance: If necessary, increase the resistance of the load to ensure the amplifier isn’t overdriven. Buffer the Output: If you need to drive a low impedance load, consider using a buffer amplifier or a dedicated output driver to prevent saturation.Summary of Solutions:
Limit Input Voltage: Ensure input signals stay within the amplifier’s operating range. Verify Power Supply: Provide adequate supply voltage to avoid output limitations. Adjust Gain: Use a proper gain setting resistor to avoid amplifying small signals too much. Reduce Input Differential Voltage: Make sure the input voltage difference is within specifications. Check Output Load: Ensure the load impedance is suitable for the amplifier’s capabilities.By following these guidelines and adjusting the conditions that cause saturation, you can significantly improve the performance of your AD620BRZ amplifier and achieve more accurate, reliable signal amplification.