Generating a Simple Negative Power Supply Using an Operational Amplifier

Creating a simple negative power supply can be achieved using a few different methods, but one straightforward approach involves using an operational amplifier (op-amp) in an inverting configuration. This method is efficient and relatively simple to implement, making it suitable for a wide range of electronic applications.

Method: Using an Op-Amp as an Inverter

Components Needed

Operational Amplifier (e.g., LM358) Resistors (two identical resistors, e.g., 10kΩ) A positive voltage source (e.g., 12V) (Optional) Capacitors for stability Breadboard and jumper wires

Circuit Description

Op-Amp Configuration: Set up the op-amp in an inverting configuration.

Connect the positive voltage source to the op-amp's positive power supply pin (V ). Connect the non-inverting input (V ) to ground. Connect the output of the op-amp to the inverting input (V-) through one resistor (R1). Connect another resistor (R2) from the inverting input to the input voltage source (Vin). The output of the op-amp will provide a negative voltage relative to ground.

Circuit Diagram Vin: 12V R2 R1 Vout: -12V Op-Amp GND

Steps to Create the Circuit

Place the Op-Amp on a Breadboard. Connect R1 and R2 as described in the configuration. Connect your positive voltage source to Vin. Make sure the non-inverting input is grounded. Connect the op-amp’s power pins to the positive voltage source and ground. Use a multimeter to measure the output voltage. The output should be negative relative to ground.

Notes

The output voltage will be approximately the negative of the input voltage, depending on the resistor values used (if R1 R2, Vout ≈ -Vin). Ensure that the op-amp you choose can handle the supply voltage and output current for your application. This setup can serve as a virtual ground for circuits requiring a negative supply voltage.

Alternative Methods

There are other methods to generate a negative voltage, such as using a charge pump circuit with capacitors and diodes, or using a dedicated negative voltage regulator like the LM7905 for more stable and precise negative voltages.

Conclusion

This method provides a simple and effective way to generate a negative voltage for various electronic applications, from basic circuits to more complex systems requiring a negative supply voltage.