An inverting amplifier is a fundamental electronic circuit commonly used in analog electronics to amplify signals. It's a type of operational amplifier (op-amp) configuration that produces an output that is an inverted (180-degree phase shifted) and amplified version of the input signal. In other words, if the input voltage increases, the output voltage decreases, and vice versa. This inversion of the input signal is where the term "inverting" comes from.
The basic inverting amplifier circuit consists of an op-amp and two resistors:
Operational Amplifier (Op-Amp): The op-amp is a high-gain differential amplifier with two input terminals (inverting and non-inverting) and one output terminal. The ideal op-amp has infinite input impedance and zero output impedance, which means it doesn't draw any current from the input source and can drive any load connected to its output.
Input Terminal (Inverting Input): The input signal is applied to the inverting input terminal of the op-amp. The inverting input is usually marked with a negative sign (-).
Feedback Resistor (Rf): This resistor connects the output of the op-amp back to its inverting input terminal. The junction between the inverting input and the feedback resistor is also connected to the ground (0V reference).
Input Resistor (Rin): This resistor is connected between the inverting input terminal and the input signal source.
The working principle of an inverting amplifier is as follows:
When an input voltage is applied to the inverting terminal of the op-amp, a current flows through the input resistor (Rin), causing a voltage drop across it.
This voltage drop is amplified by the op-amp, and the amplified voltage is fed back to the inverting terminal through the feedback resistor (Rf).
The op-amp tries to maintain its inverting and non-inverting input terminals at the same voltage level. Due to the feedback mechanism, the inverting input terminal effectively becomes a virtual ground, and the op-amp adjusts its output voltage to ensure this equality.
The output voltage of the inverting amplifier is given by the equation: Vout = - (Rf / Rin) * Vin, where Vin is the input voltage.
By adjusting the values of the feedback resistor (Rf) and the input resistor (Rin), you can control the gain of the inverting amplifier. The gain is determined by the ratio of the two resistors: Gain (Av) = - Rf / Rin. It's worth noting that the negative sign in the gain equation indicates the inversion of the signal.
In summary, an inverting amplifier circuit using an op-amp is a versatile tool for amplifying and inverting input signals. Its gain can be easily adjusted by changing the resistor values, making it a valuable component in various analog signal processing applications.