Op-Amp Circuit Analysis

11 Questions

What is the output phase of an ideal op-amp when the input signal is inverting?

180° out of phase with input signal

Which electrical characteristic is not exhibited by an ideal op-amp?

Infinite output resistance

Why does an ideal op-amp require infinite bandwidth?

Signals can be amplified without attenuation

Why does an ideal op-amp have infinite voltage gain?

To obtain finite output voltage

What is the output voltage for an ideal op-amp when the inverting terminal is zero?

Option a

How is the output voltage obtained for an ideal op-amp?

Amplifies the difference between the two input voltages

For Vd > ±4VT, what function will the differential amplifier act as?

Limiter

How are arbitrary signals represented when applied to the input of a transistor?

Sum and Difference of VCM & VDM

Define the total current (IQ) equation in differential amplifier with constant current bias.

IQ = 1/R3 × (VEE × R2 / (R1 + R2))

Constant current source in a differential amplifier is also called a current mirror.

True

When will the mirror effect be valid?

β ≫ 1

Study Notes

Here are the study notes for the text:

Differential Amplifier*
A differential amplifier is a type of op-amp configuration that amplifies the difference between two input signals.
It has two input terminals, one inverting and one non-inverting.
The output voltage is proportional to the difference between the two input signals.
Characteristics of Ideal Op-Amp*
Infinite voltage gain
Infinite bandwidth
Zero output resistance
Infinite input resistance
Zero input current
Types of Op-Amp Configurations*
Inverting Amplifier:
- Input signal is applied to the inverting terminal.
- Output voltage is inverted and amplified.
Non-Inverting Amplifier:
- Input signal is applied to the non-inverting terminal.
- Output voltage is amplified but not inverted.
Differential Amplifier:
- Two input signals are applied to the input terminals.
- Output voltage is proportional to the difference between the two input signals.
Differential Mode Gain and Common Mode Gain*
Differential Mode Gain: The gain of the amplifier when the input signals are differential.
Common Mode Gain: The gain of the amplifier when the input signals are common mode.
Common Mode Rejection Ratio (CMRR)*
The ratio of the differential mode gain to the common mode gain.
CMRR = 20 log (ADM / ACM)
A higher CMRR indicates better rejection of common mode signals.
Improving CMRR*
Increasing the differential mode gain (ADM) improves CMRR.
Decreasing the common mode gain (ACM) improves CMRR.
Constant Current Source*
A constant current source is used in differential amplifiers to improve CMRR.
The current source is called a "current mirror".
Open-Loop Configuration*
An open-loop configuration is not used in linear applications because the output switches between positive and negative saturation levels.
Any positive input signal drives the output to saturation level.