# Operational Amplifiers Study notes Part-2

By Chandani Prakash|Updated : April 23rd, 2021

In this article, you will find the Study Notes on Operational Amplifiers which will cover the topics such as Schmitt Trigger, Precision Rectifier, Instrumentation Amplifier, Astable Multivibrator, Bistable Multivibrator, Monostable Multivibrator

In this article, you will find the Study Notes on Operational Amplifiers which will cover the topics such as Schmitt Trigger, Precision Rectifier, Instrumentation Amplifier, Astable Multivibrator, Bistable Multivibrator, Monostable Multivibrator

1. Schmitt Trigger:

The Schmitt trigger or Bistable multivibrator uses positive feedback with loop gain greater than unity to produce a bistable characteristics as shown below

Inverting Schmitt Trigger

Here,

Voltage Transfer Characteristics as input voltage increases

Voltage Transfer Characteristics as input voltage decreases

Net Voltage Transfer Characteristics showing Hysteresis Effect

Here,

2. Precision Rectifier:

Below figure shows a Precision rectifier and its input and output waveform.

For positive value of Vi, diode will be ON. and for negative value of Vi, diode will be OFF as shown below.

Equivalent Circuit of Precision Rectifier for Positive value of Vi

Equivalent Circuit of Precision Rectifier foe Negative value of Vi

From the above circuit, we observe that

For Vi > 0, diode will be OFF, so V0 = 0

For Vi < 0, diode will be ON, so V0 = Vi

Thus, we obtain the voltage transfer characteristics for the precision rectifier as shown below

Voltage Transfer Characteristics for Precision Rectifier

3.Instrumentation Amplifier:

It consists of two non-inverting amplifiers and one difference amplifier.

Instumentation Amplifier

The output voltages of the two non-inverting amplifiers are given by:

Thus, we obtain the net output of the instrumentation amplifier as

4. Astable Multivibrator:

Astable Multivibrator

Waveform

Here,

TC = charging time

Td = discharging time

V0 = Vfinal + [Vinitial – Vfinal]e–t/RC

Here,

Vinitial = βVsat

Vfinal = –Vsat

V0 = –βVsat

–βVsat = –Vsat + [βVsat + Vsat]e–Td/RC

(1 – β) Vsat = (1 + β) Vsat .e–Td/RC

5. Bistable Multivibrator:

Bistable Multivibrator

Here, a to b changes only after triggering and before triggering, it will be

constant = +Vsat

6.Monostable Multivibrator:

Monostable Multivibrator

Waveform

Time Period of Monostable Multivibrator:

TP=0.693RC

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