Operational Amplifier Fundamentals

Operational Amplifier Fundamentals

• Operational amplifiers (op-amps) are integrated circuits designed to amplify weak electrical signals.
• Op-amps have two input pins and one output pin. The output voltage is the amplified difference between the two input voltages.
• Op-amps can be used in various configurations, including inverting, non-inverting, summing, and differential amplifier circuits.
• The gain of an op-amp can be very high, typically in the range of 10⁵ to 10⁶.
• The open-loop voltage gain (differential gain) of an op-amp is the gain of the internal amplifier in the device.
• The common mode rejection ratio (CMRR) is the ability of an op-amp to reject a common-mode signal.

Op-Amp Specifications

• Input impedance (Ri): The input impedance of an ideal op-amp is infinite.
• Output impedance (Ro): The output impedance of an ideal op-amp is zero.
• Open-loop gain (A): The open-loop gain of an ideal op-amp is infinite.
• Bandwidth: The bandwidth of an ideal op-amp is infinite.
• Slew rate: The rate at which an op-amp can react to a change in input level.
• Input offset current (Ios): The difference between input bias currents.
• Input bias current (IBIAS): The average of the two input currents.
• Offset voltage: The voltage difference between the input terminals when the output is zero.
• Op-amp IC 741 specification (example): Includes input impedance, output impedance, open-loop gain, offset voltage, slew rate, and CMRR(common mode rejection ratio).

Filter Types

• Filters are circuits that pass (or amplify) certain frequencies while attenuating others.
• Filter types include low-pass, high-pass, band-pass, and band-stop filters.
• Low-pass filters allow low-frequency signals to pass and block high-frequency signals.
• High-pass filters allow high-frequency signals to pass and block low-frequency signals.
• Band-pass filters pass signals only within a certain frequency band, rejecting those outside it.
• Band-stop filters block signals only within a certain frequency band.

Passive vs. Active Filters

• Passive filters only use passive components (resistors, capacitors, inductors).
• Active filters use active components like operational amplifiers in addition to passive components.
• Active filters can achieve higher gain and are less sensitive to load than passive filters.

Applications of Op-amps

• Active filters (low pass, high pass, band pass, band stop).
• Summing amplifier: To combine voltages from multiple inputs.
• Comparator: For comparing two input voltages.
• Integrator: To integrate an input signal.
• Differentiator: To differentiate the input signal.

Voltage Transfer Curve (VTC)

• The voltage transfer curve represents the relationship between input and output voltage of an op-amp.
• The VTC is also known as the input-output characteristic or transfer function.
• An op-amp's VTC often shows a sharp transition region between its output saturation values.

DC Power Supply

• A DC power supply typically consists of a transformer, rectifier, filter, and voltage regulator.
• AC goes into a transformer that lowers the voltage.
• Rectifier converts AC voltage to pulsating DC voltage.
• The filter circuit smooths out the pulsating DC voltage.
• Voltage regulator provides a constant DC voltage.

Additional Components and Circuits

• Virtual ground: A node in an op-amp circuit that acts as a virtual ground point, resulting in zero voltage.
• Inverting and Non-Inverting Amplifier: Circuits which utilize the operational amplifiers.
• Differential amplifier: amplifies the difference between two input signals.

Test your knowledge on the fundamentals of operational amplifiers (op-amps), including their configurations, specifications, and gain characteristics. This quiz will cover essential concepts such as input and output impedance, open-loop gain, and common mode rejection ratio.