A non-inverting amplifier is a fundamental electronic circuit used to amplify an input signal's voltage while maintaining the same polarity. In simpler terms, it increases the amplitude of a signal without inverting its direction. This type of amplifier is widely used in various applications, including audio amplification, signal conditioning, and sensor interfacing.
The basic configuration of a non-inverting amplifier consists of an operational amplifier (op-amp) and a few external components: two resistors and a power supply. Here's how it works:
Operational Amplifier (Op-Amp): An op-amp is a high-gain, differential voltage amplifier with two input terminals (inverting and non-inverting) and one output terminal. The output voltage of the op-amp is a high-gain amplification of the voltage difference between its input terminals.
External Components:
Input Terminal (+): This is the non-inverting input terminal of the op-amp. The input signal is applied to this terminal.
Feedback Resistor (Rf): This resistor connects the output of the op-amp to the inverting input terminal (negative feedback configuration). It determines the amplification factor of the circuit.
Input Resistor (R1): This resistor is connected between the non-inverting input terminal and the input signal source. It forms a voltage divider with the feedback resistor and helps set the gain of the amplifier.
Power Supply: The op-amp requires a dual power supply (positive and negative) to operate properly. However, for simplicity, we often assume a single positive power supply and a virtual ground at the midpoint of the supply voltage.
Operation:
When an input voltage (Vin) is applied to the non-inverting input terminal, the op-amp's output responds by adjusting to a voltage that minimizes the voltage difference between its two inputs (inverting and non-inverting).
The voltage at the inverting input terminal is determined by the feedback resistor (Rf) and the voltage at the output terminal. The feedback mechanism drives the inverting input to a voltage that matches the non-inverting input.
The gain (Av) of the amplifier is determined by the ratio of the feedback resistor (Rf) to the input resistor (R1), according to the formula: Av = 1 + (Rf / R1).
The output voltage (Vout) of the amplifier is given by: Vout = Av * Vin.
In summary, the non-inverting amplifier provides signal amplification while preserving the input signal's polarity. By adjusting the values of the input and feedback resistors, you can control the amplification factor of the circuit. Keep in mind that real-world op-amps have limitations due to factors such as bandwidth, saturation, and input/output impedance, so proper consideration of these factors is necessary when designing amplifier circuits.