A non-inverting amplifier is a type of electronic circuit commonly used to amplify a voltage signal without inverting its polarity. This means that when the input voltage increases, the output voltage also increases in the same direction. The basic design of a non-inverting amplifier involves an operational amplifier (op-amp) and a few external components.
Here's how a non-inverting amplifier works:
Operational Amplifier (Op-Amp): An op-amp is a high-gain differential amplifier with two inputs, inverting (-) and non-inverting (+), and a single output. In a non-inverting amplifier configuration, the non-inverting input (+) is connected to the input voltage source, while the inverting input (-) is usually grounded or connected to a reference voltage.
Feedback Network: The key to the operation of a non-inverting amplifier is the feedback network. This network consists of two resistors: one connected between the op-amp's output and the inverting input (-), and another connected between the inverting input and ground (or a reference voltage). The junction between these two resistors is the output of the amplifier.
Amplification Equation: The voltage gain (amplification) of a non-inverting amplifier is determined by the ratio of the feedback resistor (Rf) to the input resistor (Rin), plus 1. The amplification equation is as follows:
Gain (A) = 1 + (Rf / Rin)
The gain is always greater than 1, meaning the output voltage is larger than the input voltage.
Operational Principle: When an input voltage (Vin) is applied to the non-inverting input (+) of the op-amp, the op-amp tries to make the voltage at its inverting input (-) match the non-inverting input voltage. This causes a current to flow through the feedback resistor (Rf) and the input resistor (Rin). The voltage drop across the input resistor produces a voltage at the inverting input (-), which adjusts the op-amp's output to create a balanced condition.
Output Voltage Calculation: The output voltage (Vout) of the non-inverting amplifier is given by the following formula:
Vout = Vin * (1 + Rf / Rin)
As mentioned earlier, the output voltage is larger than the input voltage by a factor of (1 + Rf / Rin).
In summary, a non-inverting amplifier is a circuit that uses an op-amp and a feedback network of resistors to amplify an input voltage signal. The output voltage is a scaled and amplified version of the input voltage, with a gain determined by the ratio of the feedback resistor to the input resistor. This type of amplifier is widely used in various electronic applications where signal amplification without polarity inversion is required.