An inverting amplifier is a type of operational amplifier (op-amp) circuit configuration commonly used in electronics to amplify input signals while inverting their polarity. The key feature of this circuit is that the output signal is 180 degrees out of phase with the input signal. This means that if the input signal increases, the output signal decreases, and vice versa.
The basic components of an inverting amplifier circuit include an operational amplifier (op-amp), two resistors (one connected from the input to the inverting input terminal of the op-amp, and the other connected from the inverting input terminal to the output), and a feedback path that connects the output to the inverting input terminal. The non-inverting input terminal of the op-amp is typically grounded.
Here's a step-by-step explanation of how the inverting amplifier works:
Input Signal: The input signal is applied to the inverting input terminal of the op-amp through a resistor (R1). This resistor determines the input impedance of the circuit.
Feedback Path: The output of the op-amp is connected to the inverting input terminal through another resistor (R2). This creates a feedback path that allows a fraction of the output voltage to be fed back to the inverting input.
Op-Amp Behavior: An ideal op-amp has extremely high input impedance and open-loop gain, and it aims to keep the voltage difference between its inverting and non-inverting inputs close to zero. In this case, the op-amp's inverting input tries to maintain the same voltage as its non-inverting input (ground), creating a virtual short between the inverting and non-inverting terminals.
Voltage Division: The voltage at the inverting input terminal is essentially zero due to the virtual short. This means that the voltage drop across resistor R1 is the same as the voltage drop across resistor R2.
Amplification: The op-amp amplifies the voltage difference between its inputs by a very high gain (which can be considered infinite for ideal op-amps). Since the inverting input is virtually at ground potential, the voltage at the output terminal is determined by the voltage drop across resistor R2, which is proportional to the input voltage.
Inversion: Because the input signal is connected to the inverting input terminal, the output voltage is the inverted version of the input voltage. This inversion is a result of the voltage divider formed by resistors R1 and R2.
The gain of the inverting amplifier can be calculated using the ratio of the resistors, R2/R1. The negative sign indicates the inversion of the signal. The gain can be adjusted by choosing appropriate resistor values.
In practical implementations, real op-amps have limitations, such as finite gain, bandwidth, and input impedance, which can impact the performance of the circuit. However, the basic concept of an inverting amplifier remains the same, providing a simple and versatile way to amplify and invert input signals in various applications like audio amplifiers, signal processing, and instrumentation circuits.