A non-inverting amplifier is a type of operational amplifier (op-amp) circuit configuration commonly used in electronics to amplify an input voltage signal. It provides amplification while maintaining the same polarity as the input signal, hence the name "non-inverting." This means that if the input voltage increases, the output voltage also increases, and if the input voltage decreases, the output voltage decreases accordingly.
The basic non-inverting amplifier circuit consists of an operational amplifier (op-amp) and two resistors: a feedback resistor (Rf) and an input resistor (Rin). Here's how it operates:
Op-Amp Input Terminals: An op-amp has two input terminals - the inverting input (-) and the non-inverting input (+). In a non-inverting amplifier configuration, the input signal is applied to the non-inverting input terminal (+).
Feedback Resistor (Rf): The feedback resistor (Rf) is connected between the op-amp's output terminal and its inverting input (-). It provides a path for a portion of the output voltage to be fed back to the inverting input, creating a negative feedback loop.
Input Resistor (Rin): The input resistor (Rin) is connected between the non-inverting input (+) and the source of the input voltage signal.
Operation: When an input voltage (Vin) is applied to the non-inverting input (+), the op-amp attempts to make the voltage at its inverting input (-) equal to the voltage at its non-inverting input (+) due to its high gain characteristics. Since the non-inverting terminal is at a known voltage (Vin), the op-amp adjusts its output (Vout) to ensure that the inverting terminal voltage matches the non-inverting terminal voltage.
Negative Feedback: The feedback resistor (Rf) helps stabilize the circuit and determine the amplification factor. A portion of the output voltage is fed back to the inverting input, creating negative feedback. This causes the op-amp to adjust its output to minimize the voltage difference between the inverting and non-inverting inputs.
Gain Calculation: The gain (voltage amplification) of the non-inverting amplifier is determined by the ratio of the feedback resistor (Rf) to the input resistor (Rin). The gain (A) can be calculated using the formula:
A = 1 + (Rf / Rin)
The non-inverting amplifier provides a gain greater than 1, which means that the output voltage is amplified relative to the input voltage.
Output Voltage: The amplified output voltage (Vout) is obtained from the op-amp's output terminal. It is calculated as:
Vout = A * Vin
Where A is the amplification factor (gain) calculated using the resistor values.
It's important to note that in practice, the op-amp may have some limitations, such as its supply voltage range and maximum output voltage, which should be considered when designing and using non-inverting amplifier circuits.