An inverting amplifier is a fundamental electronic circuit commonly used in analog signal processing. It is built using an operational amplifier (op-amp) and a few passive components like resistors. The key characteristic of an inverting amplifier is that the output signal is the inverted (180-degree phase shift) version of the input signal. In other words, if the input signal goes up, the output signal goes down, and vice versa.
Here's how the inverting amplifier circuit works:
Operational Amplifier (Op-Amp): An op-amp is a high-gain differential amplifier with two input terminals (inverting and non-inverting) and a single output terminal. The op-amp strives to make the voltage difference between its two input terminals close to zero.
Feedback Configuration: In the inverting amplifier circuit, the input signal is connected to the inverting (-) input terminal of the op-amp. The output terminal is connected back to the inverting input via a feedback resistor (Rf), and another resistor (R1) connects the inverting input to the ground (or reference voltage, typically 0V).
Voltage Gain: The gain of the inverting amplifier is determined by the ratio of the feedback resistor (Rf) to the input resistor (R1). The voltage gain (Av) can be calculated using the following formula:
Av = -Rf / R1
The negative sign indicates that the output signal is inverted compared to the input signal.
Operation: When an input voltage (Vin) is applied to the inverting input, it creates a current through R1. This current also flows through Rf due to the feedback configuration. As per the op-amp's behavior, it adjusts its output voltage to ensure that the inverting input voltage matches the non-inverting input voltage (which is usually grounded).
Output Voltage: The op-amp's output voltage is determined by the voltage drop across the feedback resistor (Rf) due to the current flowing through it. Since the inverting input is virtually at the same voltage as the non-inverting input, the output voltage is controlled by the difference between the two resistor voltages, scaled by the gain factor.
Vout = -Av * Vin
As a result, the output voltage is the inverted version of the input voltage, amplified by the voltage gain.
In summary, an inverting amplifier circuit using an op-amp and appropriate resistor values can take an input signal, invert it, and amplify it by a certain factor. This type of circuit is commonly used in applications where signal inversion and amplification are required, such as audio processing, instrumentation, and signal conditioning.