Operational Amplifiers - 2 | Analog Circuits - Electronics and Communication Engineering (ECE) PDF Download

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 EffectHere,

Precision Rectifier

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

For positive value of V_i, diode will be ON. and for negative value of V_i, diode will be OFF as shown below.
Equivalent Circuit of Precision Rectifier for Positive value of V_i

Equivalent Circuit of Precision Rectifier foe Negative value of V_i

From the above circuit, we observe that
For V_i > 0, diode will be OFF, so V₀ = 0
For V_i < 0, diode will be ON, so V₀ = V_i
Thus, we obtain the voltage transfer characteristics for the precision rectifier as shown below
Voltage Transfer Characteristics for Precision Rectifier

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

Astable Multivibrator

 Astable Multivibrator

Waveform

Here,
T_C = charging time
T_d = discharging time
V₀ = V_final + [V_initial – V_final]e^–t/RC
Here,
V_initial = βV_sat
V_final = –V_sat
V₀ = –βV_sat
∴ –βV_sat = –V_sat + [βV_sat + V_sat]e^–Td/RC
(1 – β) V_sat = (1 + β) V_sat .e^–Td/RC


Frequency of square wave generator

Bistable Multivibrator

Bistable Multivibrator

Here, a to b changes only after triggering and before triggering, it will be
constant = +V_sat  

Monostable Multivibrator

 Monostable Multivibrator

Waveform

Time Period of Monostable Multivibrator:
T_P = 0.693RC