9.11 : Frequency Response of Op Amp Circuits

Operational amplifiers (op-amp) are used in signal conditioning, filtering, or for performing mathematical operations such as addition, subtraction, integration, and differentiation. The frequency response of an op-amp is an important aspect that describes how the gain of the amplifier varies with frequency.

Frequency Response and Gain:

The gain of the op-amp, A(ω), is not a constant but a function of the input signal frequency. An op-amp can maintain a constant gain at low frequencies, known as the direct current (dc) gain, A₀. The gain can be shown as an equation:

ω is the input signal frequency, and ω₁ is the corner or break frequency at which the gain starts to fall below the dc gain A₀.

The Bode plot represents the logarithmic graph of the magnitude of the op-amp's gain versus frequency. It is a graphical presentation of how the gain of an op-amp diminishes at higher frequencies.

In the case of a noninverting amplifier, the circuit configuration has the input voltage applied to the non-inverting terminal of the op amp, leading to an amplified output voltage that is in phase with the input. This circuit's gain is influenced by the op amp's frequency response and the ratio of the resistances R₁ and R₂ used in the circuit. The network function of the noninverting amplifier is given by:

Where K is the ideal gain of the amplifier as is written as:

The frequency response of an operational amplifier is essential in determining how effectively it can amplify signals at different frequencies. The concept of gain versus frequency and the gain-bandwidth product are used in the design and application of op-amp circuits in electronic devices.