Operational amplifiers, or OpAmps, are fundamental components in electronic circuits, known for their versatility in signal processing applications. These integrated circuits can amplify voltage signals, making them essential in filtering, measuring, and analog computing operations. A non-inverting amplifier is a specific configuration of an OpAmp where the input voltage is applied to the non-inverting input, resulting in an output voltage that is in phase with the input.
Gain Equation for a Non-Inverting Amplifier
The gain (Av) of a non-inverting amplifier is determined by the resistance values of the feedback resistor (Rf) and the resistor connected to the ground (Rg). The gain dictates how much the input signal is amplified at the output. The equation for the gain is:
In the context of the practical exercise, where a potentiometer is used to vary the resistance, Rf would be the portion of the potentiometer acting as the feedback resistor, and Rg would be the portion connected to ground. By adjusting the potentiometer, you effectively change the values of Rf and Rg, thereby adjusting the gain.
Practical Experiment: Building a Non-Inverting Amplifier
Required Materials
- An OpAmp, specifically the OP37, chosen for its availability within the ADALP2000 Analog Parts Kit, allowing for experimentation without the fear of damage.
- Resistors and a potentiometer for adjustable resistance ratios.
- Red Pitaya for power supply (5V and -4V) and signal generation.
- Standard laboratory equipment including wires (Ethernet cables for optimal performance), alligator clips, and a breadboard.
Procedure
- Circuit Assembly: The OP37 OpAmp connects to the Red Pitaya’s 5V (U+) and -4V (U-) pins for power. The inverting and non-inverting inputs, along with the output, are configured as per the schematic. A single potentiometer replaces the dual-resistor setup for R1 and R2, simplifying the adjustment of the resistor ratio.
- Signal Input: Connect the Red Pitaya’s sine wave output to the amplifier's input, setting all probes to x10 mode for clarity.
- Observation: Adjust the potentiometer while monitoring the output. Note the conditions under which maximum amplification and saturation occur, and whether the inverting and non-inverting inputs maintain equal voltage throughout.
Voltage Follower Configuration
The voltage follower or unity gain buffer represents a specialized variant of the non-inverting amplifier, characterized by a gain of 1 (Av=1). Achieved by setting Rf to 0 ohms and eliminating Rg, this configuration is utilized to preserve signal amplitude while offering high input impedance and low output impedance.
Conclusion
This exercise demystifies the operational principles and practical construction of a non-inverting amplifier, demonstrating the impact of variable resistance on gain. Through hands-on assembly and testing of the amplifier circuit, we delve into the nuances of OpAmp functionality, underscoring the critical role of such amplifiers in a myriad of electronic applications.