A non-inverting amplifier is a type of electronic circuit commonly used in analog signal processing. Its primary function is to amplify an input signal without inverting its polarity. In other words, if the input signal increases, the output signal also increases, and if the input signal decreases, the output signal decreases, maintaining the same relative polarity.
The basic structure of a non-inverting amplifier consists of an operational amplifier (op-amp) and a few passive components like resistors. An operational amplifier is a high-gain voltage amplifier with two input terminals (inverting and non-inverting) and one output terminal. The non-inverting amplifier configuration is set up by connecting the non-inverting input terminal of the op-amp to the input signal source and using feedback through a resistor network to control the gain.
Here's how a non-inverting amplifier works:
Input Connection: The input signal (Vin) is connected to the non-inverting (+) input terminal of the op-amp.
Feedback Network: A resistor (R1) is connected between the output terminal of the op-amp and the inverting (-) input terminal. Another resistor (R2) is connected between the inverting input terminal and the ground (or reference) voltage.
Amplification Principle: The key principle of the non-inverting amplifier is the virtual short-circuit property of the op-amp's input terminals. This property ensures that the voltage at the inverting and non-inverting terminals is virtually the same. Due to this, the voltage at the inverting terminal, which is also the junction between R1 and R2, is approximately equal to the input voltage Vin.
Feedback Mechanism: The op-amp amplifies the voltage difference between its input terminals. Since the voltage at the inverting terminal is approximately the same as Vin, the voltage at the junction of R1 and R2 is also Vin. The voltage across resistor R2 (between the inverting input and ground) is therefore (Vin - 0), which is simply Vin.
Output Voltage Calculation: The op-amp amplifies this voltage difference between the inverting and non-inverting terminals by a factor known as the gain (A). The gain of a non-inverting amplifier is calculated using the formula A = 1 + (R2 / R1). Therefore, the output voltage (Vout) can be calculated as Vout = Vin * (1 + R2 / R1).
Signal Amplification: As the input voltage changes, the op-amp adjusts its output voltage to ensure that the voltage at the inverting terminal matches the non-inverting terminal. This results in an amplified output voltage that maintains the same polarity as the input signal.
In summary, a non-inverting amplifier is a useful circuit for amplifying analog signals while preserving their original polarity. It is commonly used in various applications such as audio amplification, signal conditioning, and sensor interfacing.