Ideal-Practical Opamp

Characteritic parameters

Differential Amplifier

Virtual Short in Opamp

Instrumentation Amplifier

Sqare Wave Generator

Schmitt trigger

741 Opamp PIN Diagram

Voltage follower- sample and hold

Lag and Lead Compensators

Bridge amplifier

Precision diode- Halfwave Rectifier

Peak and Zero Crossing Detector

Integrator-Differentiator

Log and Anti-Log Amplifiers

Inverting- Non inverting Amplifiers

Oscillators

**Op amp Lag compensator**

**Definition**

A lag compensator is one which adds a pole the system and is used to improve the steady state response of the system. A lag compensator provides phase lag (negative phase) in the frequency response of system.

**Op amp Lag compensator Circuit operation**

A simple lag compensator realized using Op amp is shown below

Using the concept of virtual ground the opamp lag compensator can be redrawn as shown in the figure

Using voltage divider principle the transfer function of the system is

** V _{o}/V_{s} =(1+s*C*R_{1})/(1+(R_{1}+R_{2})*s*C)**,

hence the phase added to system is given as

** Ω = tan ^{-1}(ω*C*R_{1}) – tan^{-1}(ω*C*(R_{1}+R_{2})) **

Since R_{1}<R_{1}+R_{2} and tan^{-1}(x) is increasing function (if a <b, tan^{-1}(a)< tan^{1}(b)) Ω is negative (phase lag).

**Op amp Lead compensator**

**Definition**

A lead compensator is one which adds a zero the system and is used to improve the transient response of the system. A lead compensator provides phase lead (positive phase) in the frequency response of system.

**Op amp Lag compensator Circuit operation**

A simple lead compensator realized using Op amps is shown below

Using the concept of virtual ground the opamp lag compensator can be redrawn as shown in the figure

Using voltage divider principle the transfer function of the system is

**V _{o}/V_{s}=(1+s*C*R_{1})/(1+(R_{1}*R_{2}/(R_{1}+R_{2}))*s*C)**,

hence the phase added to system is given as

** Ω =tan ^{-1}(ω*C*R_{1}) -tan^{-1}(ω*C*R_{1}*R_{2}/(R_{1}+R_{2}))**.

Since R_{1} > R_{1}*R_{2}/(R_{1}+R_{2}) Ω is positive(phase lead).