How to Use OP37 - Low Noise, Precision, High Speed Op Amp: Examples, Pinouts, and Specs

The OP37, manufactured by Analog Devices, is a high-performance operational amplifier designed for applications requiring low noise, precision, and high-speed signal amplification. With its superior characteristics, the OP37 is widely used in instrumentation, audio processing, medical devices, and other precision signal processing applications.

• High-precision instrumentation amplifiers
• Audio preamplifiers and equalizers
• Medical instrumentation (e.g., ECG, EEG amplifiers)
• Data acquisition systems
• Active filters and integrators
• High-speed signal processing circuits

The OP37 is available in an 8-pin package. The pinout and descriptions are as follows:

1. Power Supply: Connect the OP37 to a dual power supply (e.g., ±15 V) for optimal performance. Ensure the supply voltage does not exceed the specified range (±18 V maximum).
2. Input Connections:
   • Connect the signal source to the non-inverting input (Pin 3) or the inverting input (Pin 2), depending on the desired configuration (non-inverting or inverting amplifier).
   • Use appropriate resistors to set the gain of the amplifier.
3. Offset Adjustment: If precise offset voltage adjustment is required, connect a 10 kΩ potentiometer between Offset Null 1 (Pin 1) and Offset Null 2 (Pin 5), with the wiper connected to the negative supply (Pin 4).
4. Output Load: Ensure the load connected to the output (Pin 6) does not exceed the amplifier's drive capability. For best performance, use a load impedance of at least 2 kΩ.
5. Bypass Capacitors: Place decoupling capacitors (e.g., 0.1 µF ceramic and 10 µF electrolytic) close to the power supply pins (Pins 4 and 7) to minimize noise and ensure stability.

• Avoid exceeding the input voltage range to prevent damage or distortion.
• Use proper grounding techniques to minimize noise and interference.
• For high-frequency applications, consider adding a small capacitor (e.g., 10 pF) across the feedback resistor to improve stability.
• Ensure the layout of the PCB minimizes parasitic capacitance and inductance, especially in high-speed applications.

The OP37 can be used to amplify analog signals for an Arduino UNO. Below is an example of a non-inverting amplifier circuit with a gain of 10.

• Connect the OP37's V+ (Pin 7) to +12 V and V- (Pin 4) to -12 V.
• Connect the signal source to the non-inverting input (Pin 3).
• Use a resistor divider to set the gain: R1 = 1 kΩ (feedback resistor), R2 = 100 Ω (resistor to ground).
• Connect the output (Pin 6) to an analog input pin on the Arduino (e.g., A0).

// Arduino code to read amplified signal from OP37 and display it
// on the serial monitor.

const int analogPin = A0; // Analog pin connected to OP37 output
int sensorValue = 0;      // Variable to store the analog reading

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
}

void loop() {
  sensorValue = analogRead(analogPin); // Read the analog value
  float voltage = sensorValue * (5.0 / 1023.0); // Convert to voltage
  Serial.print("Amplified Voltage: ");
  Serial.print(voltage);
  Serial.println(" V");
  delay(500); // Wait for 500 ms before the next reading
}

1. No Output Signal:

   • Verify the power supply connections and ensure the voltage is within the specified range.
   • Check the input signal and ensure it is within the input voltage range of the OP37.
   • Confirm that the feedback network is correctly connected.

2. Output Distortion:

   • Ensure the load impedance is not too low (minimum 2 kΩ recommended).
   • Check for excessive input signal levels that may cause clipping.

3. High Noise Levels:

   • Use proper grounding and shielding techniques to minimize interference.
   • Add bypass capacitors close to the power supply pins.

4. Instability or Oscillation:

   • Add a small capacitor (e.g., 10 pF) across the feedback resistor to improve stability.
   • Ensure the PCB layout minimizes parasitic capacitance and inductance.

Q: Can the OP37 operate with a single power supply?
A: Yes, the OP37 can operate with a single supply, but the input and output signals must remain within the specified voltage range. A virtual ground may be required for proper operation.

Q: What is the maximum gain I can achieve with the OP37?
A: The OP37 is optimized for gains of 5 or higher. For lower gains, consider using a different operational amplifier.

Q: How do I minimize offset voltage in my circuit?
A: Use the offset null pins (Pins 1 and 5) with a potentiometer to fine-tune the offset voltage.