OPERATIONAL OPERATIONAL AMPLIFIERAMPLIFIER

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OPERATIONAL OPERATIONAL AMPLIFIERAMPLIFIER

OP- AMP is a solid state device capable of sensing and amplifying dc and ac input signals.

OP- AMP is a high gain differential amplifier with nearly ideal external characteristics.

OP-AMP OP-AMP COMPONENTSCOMPONENTS

• TransistorsTransistors

• ResistorsResistors

• DiodesDiodes

• CapacitorsCapacitors

OP-AMP STAGESOP-AMP STAGES

NON INVERTING

INPUT

INVERTING INPUT

OUTPUT

DUAL-INPUT BALANCED

OUTPUT DIFFERENTIAL

AMPLIFIER

DUAL-INPUT UNBALANCED

OUTPUT DIFFERENTIAL

AMPLIFIER

EMITTER FOLLOWER

WITH CONSTANT CURRENT SOURCE

COMPLEMENTARY SYMMETRY PUSH-PULL AMPLIFIER

CIRCUIT SYMBOLCIRCUIT SYMBOL

The OP-AMP is represented by a triangular symbol.

It has two input and one output terminals.

EQUIVALENT EQUIVALENT CIRCUITCIRCUIT

Non InvertingInput

Inverting Input

Output

Vout = G(v1-v2)

1

2

CHARACTERSTICS OF CHARACTERSTICS OF IDEAL IDEAL OP-AMPOP-AMPCHARACTERISTICS IDEAL VALUES

Voltage gain ∞ Input impedance

∞

Output impedance

0

Bandwidth ∞ Input offset voltage

0

Input offset current

0

Slew rate ∞ CMRR ratio ∞

OP-AMP OP-AMP CONFIGURATIONSCONFIGURATIONS

INVERTING OP-AMPINVERTING OP-AMP

• An inverting amplifier uses negative feedback

to invert and amplify a voltage.

Output is 180° out of phase.

For the non-inverting amplifier the input is

connected to the non-inverting input.Output is in phase with the input.

NON-INVERTING OP-NON-INVERTING OP-AMPAMP

A particular form of this amplifier is when the

feedback loop is a short circuit, I.e. R2 = 0. Then

the voltage gain is 1, such an amplifier is called a

Voltage Follower.

(GROUND)

VOLTAGE FOLLOWERVOLTAGE FOLLOWER

Vout = Vin

•An inverting amplifier can accept two or more inputs

and produce a weighted sum

At X, I = IA + IB + IC = -(VA/RA+VB/RB+VC/RC)

SUMMING SUMMING AMPLIFIERAMPLIFIER

C

C

2B

B

2A

A

2out .V

R

R.V

R

R.V

R

RV

VA

VB

VC

SUBTRACTOR SUBTRACTOR AMPLIFIERAMPLIFIER

Amplifies the difference between the two voltages applied at the two ends of the amplifier.

Neither of the input lines is grounded. Noise appearing at both the input terminals

does not appear at the output.

Integrator produces an output voltage which is

proportional to the time integral of the input voltage

Integrating both sides gives

INTEGRATOR INTEGRATOR AMPLIFIERAMPLIFIER

.dtVRC

1dV inout

2

1

t

tin1out2out.dtV

RC

1tVtV

The function of an differentiator is to give an

output voltage which is proportional to the rate of input voltage.

DIFFERENTIATOR DIFFERENTIATOR AMPLIFIERAMPLIFIER

PRACTICAL PRACTICAL APPLICATIONSAPPLICATIONS• Perform math operationsPerform math operations

• ADC and DACADC and DAC

• Sign changerSign changer

• Voltage RegulationVoltage Regulation

• Pulse generatorsPulse generators

• Wave generator Wave generator