Explain the operation of an inverting amplifier circuit.
1 Answer
An inverting amplifier is a basic electronic circuit used to amplify an input signal while inverting its polarity. It is commonly implemented using an operational amplifier (op-amp) with a few external components. The input signal is applied to the inverting input terminal of the op-amp, and the output is taken from the output terminal. Let's go through the operation step by step:
Basic Circuit Configuration:
The inverting amplifier circuit consists of three main components:
Operational Amplifier (Op-Amp): A high-gain differential amplifier with two inputs (inverting and non-inverting) and one output.
Feedback Resistor (Rf): Connected between the output and the inverting input terminal of the op-amp.
Input Resistor (Rin): Connected between the inverting input terminal and the input signal source.
Ideal Op-Amp Assumptions:
In the analysis of the inverting amplifier circuit, we make the following ideal op-amp assumptions:
Infinite Input Impedance: The inverting input terminal draws no current.
Zero Input Current: The input current flowing into the op-amp is negligible.
Infinite Open-Loop Gain: The op-amp has an infinitely high gain.
Zero Output Impedance: The output impedance of the op-amp is negligible.
Operation:
When an input voltage (Vin) is applied to the inverting input terminal of the op-amp, a current flows through the input resistor (Rin). Since the op-amp's inverting input draws no current, all of the current flowing through Rin also flows through the feedback resistor (Rf).
The op-amp's high gain amplifies the voltage across the feedback resistor. Since the voltage at the inverting input terminal is almost equal to the voltage at the non-inverting input terminal (due to the virtual short concept of the ideal op-amp), the voltage at the inverting input remains very close to 0V (virtual ground).
The feedback mechanism causes the op-amp to adjust its output voltage in such a way that the voltage at the inverting input remains at virtual ground. To achieve this, the output voltage (Vout) becomes such that the voltage drop across the feedback resistor (Rf) is equal in magnitude but opposite in polarity to the input voltage (Vin). As a result, the output voltage is inverted with respect to the input voltage.
Mathematically, the gain (Av) of the inverting amplifier can be expressed as:
Av = -Rf / Rin
Since the output voltage is an inverted version of the input voltage, the gain is typically negative, indicating a phase inversion.
Application:
Inverting amplifiers are widely used in signal processing, audio applications, instrumentation, and many other electronic circuits where signal amplification with inverted polarity is required. The gain of the amplifier can be easily controlled by adjusting the values of the feedback and input resistors.
It's essential to choose appropriate resistor values and ensure that the op-amp is within its linear operating range to achieve accurate and stable amplification without distortion. Additionally, real-world op-amps may have finite input impedance, non-zero input currents, and finite open-loop gain, which should be considered in practical designs.
Basic Circuit Configuration:
The inverting amplifier circuit consists of three main components:
Operational Amplifier (Op-Amp): A high-gain differential amplifier with two inputs (inverting and non-inverting) and one output.
Feedback Resistor (Rf): Connected between the output and the inverting input terminal of the op-amp.
Input Resistor (Rin): Connected between the inverting input terminal and the input signal source.
Ideal Op-Amp Assumptions:
In the analysis of the inverting amplifier circuit, we make the following ideal op-amp assumptions:
Infinite Input Impedance: The inverting input terminal draws no current.
Zero Input Current: The input current flowing into the op-amp is negligible.
Infinite Open-Loop Gain: The op-amp has an infinitely high gain.
Zero Output Impedance: The output impedance of the op-amp is negligible.
Operation:
When an input voltage (Vin) is applied to the inverting input terminal of the op-amp, a current flows through the input resistor (Rin). Since the op-amp's inverting input draws no current, all of the current flowing through Rin also flows through the feedback resistor (Rf).
The op-amp's high gain amplifies the voltage across the feedback resistor. Since the voltage at the inverting input terminal is almost equal to the voltage at the non-inverting input terminal (due to the virtual short concept of the ideal op-amp), the voltage at the inverting input remains very close to 0V (virtual ground).
The feedback mechanism causes the op-amp to adjust its output voltage in such a way that the voltage at the inverting input remains at virtual ground. To achieve this, the output voltage (Vout) becomes such that the voltage drop across the feedback resistor (Rf) is equal in magnitude but opposite in polarity to the input voltage (Vin). As a result, the output voltage is inverted with respect to the input voltage.
Mathematically, the gain (Av) of the inverting amplifier can be expressed as:
Av = -Rf / Rin
Since the output voltage is an inverted version of the input voltage, the gain is typically negative, indicating a phase inversion.
Application:
Inverting amplifiers are widely used in signal processing, audio applications, instrumentation, and many other electronic circuits where signal amplification with inverted polarity is required. The gain of the amplifier can be easily controlled by adjusting the values of the feedback and input resistors.
It's essential to choose appropriate resistor values and ensure that the op-amp is within its linear operating range to achieve accurate and stable amplification without distortion. Additionally, real-world op-amps may have finite input impedance, non-zero input currents, and finite open-loop gain, which should be considered in practical designs.