“Op-Amp” Operational Amplifier Non Inverting Amplifier Inverting Amplifier Adder –(and Subtractor using an Inverter) Differential Amplifier Integrator.

“Op-Amp”Operational Amplifier

• Non Inverting Amplifier• Inverting Amplifier• Adder

– (and Subtractor using an Inverter)

• Differential Amplifier• Integrator• Differentiator

Op-Amp name derives from early usage of these elements in performing mathematical operations in analog computers.

Three Ways to Examine Op-Amp Behavior

• Consider as an Ideal Op-Amp Component

• Consider as a Feedback Model and Examine Behavior

• Perform Conventional Circuit Analysis

VE = VIN+ - VIN-

VOUT = a * VE

VIN+

VIN-

Ideal Op-Amp Model

VE = VIN+ - VIN-

VOUT = a * VE

Behavior of Feedback Model

Behavior of Feedback Modelof

Non Inverting Amplifier

Behavior of Feedback Model

Behavior of Feedback Model

Behavior of Feedback Model

Behavior of Feedback ModelSummary

Circuit Analysis Approach

Circuit Analysis Approach

“Op-Amp”Operational Amplifier

• Non Inverting Amplifier• Inverting Amplifier• Adder

– (and Subtractor using an Inverter)

• Differential Amplifier• Integrator• Differentiator

Op-Amp name derives from early usage of these elements in performing mathematical operations in analog computers.

Differential Amplifier Circuit Analysis

a (V+ - V-)

Differential Amplifier Circuit Analysis

a (V+ - V-)

Differential Amplifier Circuit Analysis

a (V+ - V-)

Differential Amplifier Circuit Analysis

a (V+ - V-)

Differential Amplifier Circuit Analysis

a (V+ - V-)

ZF / ZG

Common Mode Rejection Ratio

vicm

v2

v1

vi1 vi2vid / 2

vid / 2

v2

v1

Original Inputs Model of inputs with common-mode and differential-mode

components

cmA

ACMRR where A is the differential

mode gain and Acm is the common mode gain

dBA

ACMRR

cmdB log20

Ideally: CMRR Typically: 60 dB CMRR 120 dB

Common Mode Rejection RatioCMRR

Assumes R2 = R4 and R1 = R3

Differential Amplifier Circuit Analysiswith Component Imbalance

Differential Amplifier Circuit Analysiswith Component Imbalance

Differential Amplifier Circuit Analysiswith Component Imbalance

Differential Amplifier Circuit Analysiswith Component Imbalance

Differential Amplifier Circuit Analysiswith Component Imbalance

The Maximum Power Transfer Theorem simply states, the maximum amount of power will be dissipated by a load resistance when that load resistance is equal to the Thevenin/Norton resistance of the network supplying the power.

To create the Thevenin Equivalent Circuit we need:

1. Value of the Thevenin Voltage Source

2. Value of the Thevenin Resistance

Input and Output Impedances of

Noninverting Op-amp Configuration

The unity gain buffer input impedance is much higher

than the op-amp input impedance Rd. The amplifier output impedance is much smaller than the op-amp

output impedance Ro.

aiR

aoR+

Rdii

Ro

RL CL

ioAvd

vd

vo

vi

+

ARARR

ARARR

ooao

ddai

/)1/(

)1(

Instrumentation Amplifier

121

2

3

4 21 vvR

R

R

Rvv refout

vout

R3

v1

R2

R3

v2

R1

R2

R4

R4

vref

1

2

3

4

12

21R

R

R

R

vv

vvG refout

Instrumentation Amplifier Example

Burr-Brown INA118

Parameters: kRRkRRR G 60 25 4321

ININrefoout VvVvvVv 12 Ref

GIN

o

R

kVG

501

VV

Ref

IN

If RG 49.9,

G 1 50,00049.9

1,003

Gain:

Instrumentation Amp (cont.)A feedback network may also be included with the instrumentation amplifier.

vout

R3

v1

R2

R3

vdiff = v2 - v12R1

R2

R4

R4

R

C

RCs

Gs

sV

sV

diff

out

1

v2