An inverting amplifier is a basic electronic circuit used to amplify an input signal with a constant gain and an inverted polarity at the output. This means that when the input signal increases, the output signal decreases, and vice versa. It is widely used in various applications, such as audio amplification, signal conditioning, and instrumentation.
The inverting amplifier circuit typically consists of an operational amplifier (op-amp) and two resistors, as shown below:
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+Vin
|
R1
|
+ ---|--- Op-Amp --- Output (Vout)
|
R2
|
GND
Here's a step-by-step explanation of how the inverting amplifier works:
Operational Amplifier (Op-Amp): An op-amp is a high-gain, differential input amplifier with two inputs, a non-inverting (+) input and an inverting (-) input. It amplifies the voltage difference between these two inputs and tries to keep them equal. In the ideal case, the gain of the op-amp is infinite.
Input Signal (+Vin): The input signal, represented as +Vin, is connected to the inverting (-) input of the op-amp.
Feedback Resistor (R1): R1 is connected between the inverting (-) input of the op-amp and the output (Vout). It provides the necessary feedback to control the amplification.
Gain Setting Resistor (R2): R2 is connected between the inverting (-) input of the op-amp and the ground (GND). It sets the gain of the amplifier circuit.
Output (Vout): The output of the inverting amplifier is taken from the junction between R1 and the inverting input of the op-amp.
Virtual Ground: In ideal op-amp analysis, the non-inverting (+) input is assumed to have no current flow (infinite input impedance). Therefore, the voltage at the inverting (-) input is virtually at the same potential as the non-inverting input, which is often referred to as "virtual ground."
The gain (A) of the inverting amplifier can be calculated using the following formula:
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A = - R2 / R1
The negative sign in the gain equation indicates the inversion of the output signal concerning the input signal.
By selecting appropriate resistor values for R1 and R2, the inverting amplifier can amplify the input signal by a desired factor. However, it's essential to ensure that the input signal remains within the acceptable range of the op-amp's power supply, as exceeding these limits may result in distortion or clipping of the output signal. Additionally, real-world op-amps have limitations that must be considered in practical circuit design, such as the maximum output voltage and current capabilities.