A non-inverting amplifier is an electronic circuit commonly used to amplify analog signals. Its primary purpose is to increase the amplitude (magnitude) of an input signal while maintaining the same polarity or phase as the original signal. In simpler terms, the output of the amplifier is a larger version of the input signal, and the waveform remains unchanged in shape.
The key components of a non-inverting amplifier circuit are an operational amplifier (op-amp) and a few passive components like resistors. Here's how it works:
Operational Amplifier (Op-Amp): An op-amp is a highly versatile integrated circuit that amplifies the difference in voltage between its two input terminals. It has a very high input impedance (resistance) and a low output impedance, making it an excellent building block for amplifiers.
Feedback Network: In a non-inverting amplifier, the input signal is applied to the non-inverting input terminal (+) of the op-amp. The inverting input terminal (-) is connected to a voltage divider network formed by resistors. This network is part of the feedback loop.
Voltage Gain: The feedback network serves to control the gain (amplification factor) of the circuit. The voltage gain (Av) of the non-inverting amplifier is given by the formula:
Av = 1 + (Rf / R1)
where Rf is the resistance of the feedback resistor and R1 is the resistance of the input resistor.
Signal Amplification: When an input signal is applied to the non-inverting input, it gets amplified by the factor determined by the feedback network. Since the input is applied to the non-inverting terminal, the output signal maintains the same phase as the input.
High Input Impedance: The non-inverting amplifier has a high input impedance due to the properties of the op-amp. This means that it doesn't draw much current from the source that provides the input signal, avoiding loading effects that could distort the original signal.
Unity Gain (Av = 1): If the feedback resistor (Rf) is set to zero (short-circuited) and the input resistor (R1) is connected to the non-inverting input, the amplifier becomes a unity gain buffer. This means the output follows the input exactly without any amplification.
Applications of non-inverting amplifiers include audio amplification, signal conditioning, instrumentation amplifiers, and any situation where you want to increase the signal strength without changing its waveform or phase. They are particularly useful when you need accurate amplification with minimal distortion and phase shifts.