Top 7 Causes of AD620 BRZ Output Clipping and How to Prevent It
The AD620BRZ is a precision instrumentation amplifier widely used in various signal processing applications. However, one common issue that users encounter is output clipping, where the amplifier’s output voltage reaches its maximum or minimum limit and cannot accurately represent the input signal. This can lead to distorted readings and system malfunction. Let’s look at the top 7 causes of AD620BRZ output clipping and how to prevent each one:
1. Excessive Input Voltage
Cause: If the input voltage exceeds the input range specification for the AD620BRZ, the amplifier will saturate, leading to output clipping. This can happen if the differential input voltage is too high for the amplifier’s input range. Solution: Ensure that the input voltage stays within the specified limits. The AD620BRZ has a differential input voltage range of ±50mV to ±100mV for optimal operation. Use voltage dividers or signal conditioning circuits to reduce the input signal if it exceeds this range.2. Insufficient Power Supply Voltage
Cause: The AD620BRZ requires a certain power supply voltage to operate correctly. If the supply voltage is too low, the amplifier cannot produce the full output voltage range, resulting in clipping. Solution: Verify that the power supply voltage meets the AD620BRZ’s specifications. For a single supply, ensure the voltage is at least 5V, and for dual supplies, ensure the voltage is symmetric around ground (e.g., ±5V, ±12V). Increasing the supply voltage within the acceptable limits will prevent clipping.3. Overdriving the Input Signal
Cause: Overdriving the input signal, where the signal is too large for the gain setting of the AD620BRZ, will push the amplifier’s output into saturation, causing clipping. Solution: Reduce the gain of the AD620BRZ or lower the input signal strength. The AD620BRZ allows gain to be adjusted via an external resistor. Lowering the gain or using attenuators before the input will keep the output from clipping.4. Incorrect Gain Resistor Value
Cause: The gain of the AD620BRZ is set using an external resistor (RG). If the value of RG is too low, the amplifier will have a high gain, causing the output to clip at lower input signal levels. Solution: Check and adjust the value of the gain-setting resistor. For normal operation, a higher RG value results in a lower gain. Be sure to choose an RG value that keeps the output within the desired range. A detailed gain equation (Gain = 1 + (50kΩ / RG)) can be used to select the correct resistor.5. Temperature Effects
Cause: High temperatures or thermal fluctuations can affect the performance of the AD620BRZ, causing the output to clip due to changes in input bias currents or offset voltages. Solution: Use the amplifier within its specified temperature range, typically -40°C to +85°C for the AD620BRZ. Consider adding heat sinks or using temperature-compensated circuits to minimize thermal issues. Also, ensure the device is properly ventilated.6. Output Load Impedance Too Low
Cause: If the output is driving a low-impedance load, such as a low-resistance resistor or a circuit with excessive current draw, the output voltage may not be able to reach its expected level, causing clipping. Solution: Ensure that the load connected to the output of the AD620BRZ has a high enough impedance. The AD620BRZ is designed to drive loads with impedances greater than 10kΩ. If needed, buffer the output with an additional op-amp to ensure the load impedance is within the amplifier’s capability.7. Improper Grounding or Power Decoupling
Cause: Poor grounding or inadequate power decoupling can introduce noise or instability into the AD620BRZ, causing unwanted clipping or distortion in the output signal. Solution: Make sure the ground connections are solid and the power supply is properly decoupled with capacitor s close to the power pins of the AD620BRZ. Use a 0.1µF ceramic capacitor and a 10µF electrolytic capacitor in parallel to reduce noise and ensure stable operation.Step-by-Step Guide to Solve Output Clipping
Check the Input Voltage: Ensure that your input signal is within the recommended range for the AD620BRZ. Use signal conditioning or scaling circuits if necessary.
Verify Power Supply Voltage: Make sure that the supply voltage is appropriate for the configuration you’re using (single or dual supply), and that it meets the device’s voltage specifications.
Adjust Gain Settings: Review the external gain resistor value (RG) and reduce the gain if the input signal is too large. A gain that's too high will lead to early saturation.
Evaluate Load Impedance: Ensure the load impedance connected to the output is not too low, as this can limit the output swing. Use a higher impedance or buffer the output.
Consider Temperature Effects: If the system is running in extreme conditions, verify that the temperature is within the operational limits and manage heat dissipation as needed.
Grounding and Power Decoupling: Ensure the circuit has solid ground connections and appropriate decoupling capacitors to prevent noise interference.
Test the System: Once you’ve adjusted these parameters, test the system to ensure that the output voltage is no longer clipping and is within the desired range.
By following these steps and understanding the root causes of output clipping, you can ensure reliable and stable operation of the AD620BRZ in your applications.