Operational Amplifiers Concepts

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Questions and Answers

What type of amplifier is used as the output stage of an op-amp?

Single-ended amplifier

Push-pull power amplifier (correct)

Differential amplifier

Class A amplifier

The non-inverting input of an op-amp is denoted with a minus (-) sign.

False (B)

What causes slight mismatches in the transistors of an op-amp?

Unequal input bias currents

In an ideal op-amp, no current is ______ from the input signal.

drawn Signup and view all the answers

Match the Op-Amp parameter to its description:

Input Bias Current = Direct current absorbed by op-amp inputs Offset Current = Difference between input currents Input Offset Voltage = Minor voltage difference between the inputs CMRR = Common-Mode Rejection Ratio Signup and view all the answers

What does the slew rate (SR) represent in an operational amplifier?

The maximum rate at which the output voltage can change. (A) Signup and view all the answers

Slew-rate limiting occurs when the slope of the sine wave is greater than the slew rate (SR).

False (B) Signup and view all the answers

What is the typical slew rate value for the IC 741 op-amp?

0.5 V/µs Signup and view all the answers

When the initial slope of the sine wave is greater than the slew rate, it leads to slew-rate __________.

distortion Signup and view all the answers

Match the following terms with their descriptions based on the content provided:

Slew Rate = Maximum rate of output voltage change Slew-rate Limiting = Output follows input up to a point and then flattens out Slew-rate Distortion = Output becomes triangular due to high input slope Open Loop Gain = Gain of an amplifier without feedback. Signup and view all the answers

What is 'input offset current' a measure of in an operational amplifier?

The difference between the biasing currents of inverting and non-inverting inputs (B) Signup and view all the answers

Input offset voltage is the error voltage that occurs when the inputs of an op-amp are grounded, resulting from differences in the $V_{BE}$ values of input transistors.

True (A) Signup and view all the answers

What is the formula for calculating Common Mode Rejection Ratio (CMRR)?

$CMRR = \frac{| A_d |}{ | A_C |}$ Signup and view all the answers

The input offset current is generally specified for ______ output voltage at 25°C temperature.

zero Signup and view all the answers

Match the following terms with their descriptions:

Input offset current = Difference in biasing currents of input transistors Input offset voltage = Error voltage when inputs are grounded CMRR = Ratio of differential to common-mode gain Signup and view all the answers

Study Notes

Operational Amplifiers

Operational amplifiers (op-amps) have two input terminals (inverting and non-inverting) and one output terminal
In a differential amplifier, the first stage produces opposite changes in the collector currents of the transistors
When the amplified signal passes from either of the transistor stages, the output of the op-amp may be out of phase with the input signal
The input for which the output is in phase with the input is called the non-inverting input; the applied signal is denoted by the (+) sign
the input for which the output is out of phase with the input is called the inverting input; denoted by the (-) sign
The output voltage (V_o) is zero

Input Offset Current

Input bias current (I_b): In an ideal op-amp, any current drawn from applied input signal is practically absorbed by the transistors, but in practical op-amps, a small amount of direct current to bias the transistors in the first differential stage is required
The input bias currents (I_b) are not equal to each other due to slight mismatch of transistors
Therefore, input bias current is not equal to the defined input bias current

Input Offset Voltage

The input offset voltage (V_io) is equal to the difference in voltage values of input transistors.
This voltage must be applied to particular input terminals to obtain zero output voltage
This is called as 'offset compensation'

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Description

This quiz covers the fundamental concepts of operational amplifiers, including their structure, input configurations, and output characteristics. It also touches on aspects of input offset current and its implications in practical applications.