A non-inverting amplifier is a type of electronic circuit used to amplify an input voltage signal. It is called "non-inverting" because the output signal maintains the same polarity as the input signal. In other words, when the input voltage increases, the output voltage also increases, and when the input voltage decreases, the output voltage decreases.
The basic configuration of a non-inverting amplifier consists of an operational amplifier (op-amp) with two external resistors: a feedback resistor (Rf) and an input resistor (Rin). The op-amp is a high-gain differential amplifier with two inputs (inverting and non-inverting) and one output.
Here's how the non-inverting amplifier works:
Op-Amp Basics: An op-amp amplifies the voltage difference between its two inputs (V+ and V-). In the case of a non-inverting amplifier, the input signal is applied to the non-inverting input (V+), while the inverting input (V-) is connected to a virtual ground, which means that it is at the same potential as the ground (0V).
Virtual Ground: The virtual ground concept arises due to the high gain of the op-amp. Since the inverting input is at 0V (ground potential), the op-amp tries to maintain V- at the same voltage as V+ (non-inverting input). Therefore, the voltage at the inverting input (V-) is practically 0V, which is known as the virtual ground.
Feedback Loop: The output of the op-amp is connected back to its inverting (-) input through the feedback resistor (Rf). This creates a negative feedback loop, which stabilizes the amplifier's gain and ensures that the output voltage follows the input voltage.
Gain Calculation: The voltage gain (Av) of the non-inverting amplifier is determined by the ratio of the feedback resistor (Rf) to the input resistor (Rin):
Av = 1 + (Rf / Rin)
Amplification: When an input voltage (Vin) is applied to the non-inverting input, the op-amp amplifies it by the calculated gain (Av) and produces an output voltage (Vout):
Vout = Av * Vin
Signal Polarity: As mentioned earlier, the output voltage (Vout) retains the same polarity as the input voltage (Vin) since the non-inverting amplifier configuration does not invert the input signal.
Overall, the non-inverting amplifier is widely used in electronic circuits to amplify signals while providing a high input impedance and low output impedance, making it an essential building block in various analog and audio applications.