EE445:Industrial Electronics. Outline Introduction Some application Comparators Integrators & Differentiators Summing Amplifier Digital-to-Analog (D/A)

EE445:Industrial Electronics

Outline Introduction Some application

Comparators Integrators & Differentiators Summing Amplifier Digital-to-Analog (D/A) Converter Difference Amplifier Instrumentation Amplifiers Audio Amplifier

Operational Amplifier (Op-Amp)

Op-amp – A high-gain dc amplifier that has high input impedance and low output impedance.

The inverting (–) input and noninverting (+) input are signal inputs.

The +V and –V inputs are supply voltage inputs.

Differential Amplifier Differential amplifier – A circuit that amplifies

the difference between two input voltages. The op-amp signal inputs are connected to a

differential amplifier. The circuit amplifies the difference between the

voltages at its inverting () and noninverting (+) inputs.

Negative Feedback Negative feedback – A type of feedback in which

the feedback signal is 180° out of phase with the input signal.

Positive Feedback Positive feedback – A type of feedback in which the

feedback signal is in phase with the input signal.

Inverting Amplifier Operation The negative feedback path in the inverting

amplifier: Reduces voltage gain (from its open-loop value). Increases bandwidth (relative to its open-loop value).

Noninverting Amplifier Operation

The negative feedback path in the noninverting amplifier:

Reduces voltage gain (from its open-loop value). Increases bandwidth (relative to its open-loop value).

Comparators Comparator – A circuit used to compare two

voltages. Comparators are typically used in conjunction

with digital circuits. A digital circuit is one designed to respond to

alternating dc voltage levels.

Comparator Operation

Level Detector Level detector – Another name for a

comparator used to compare an input voltage to a fixed dc reference voltage.

Setting the Reference Level

21

2ref RR

RVV

Smoke Detector: A Comparator Application

Integrators Integrator – A circuit whose output is

proportional to the area of the input waveform.

RC Integrator An ideal RC integrator would produce the triangular

(ramp) waveform. The practical RC integrator produces the

exponential waveform.

Op-Amp Integrator The op-amp provides a constant-current

source for the capacitor, causing it to charge at a linear rate.

Differentiators Differentiator – A circuit whose output is

proportional to the rate of change of its input signal.

Summing Amplifiers Summing amplifier – An op-amp circuit that

produces an output proportional to the sum of its input voltages.

3

3

2

2

1

1out R

V

R

V

R

VRV f

General-Class Equation General-class equation – An equation derived for a

summing amplifier that is used to predict the circuit output for any combination of input voltages.

Determine the Rf / R ratio for each branch. Represent each branch as the product of its

resistance ratio and input voltage. Write the equation as the sum of these products.

Summing Amplifier Analysis

4321out

444

333

222

111

05.01.02.0

05.0

1.0

2.0

VVVVV

VVR

R

VVR

R

VVR

R

VVR

R

f

f

f

f

Digital-to-Analog (D/A) Converter

Digital-to-analog (D/A) converter – A circuit that converts digital circuit outputs to equivalent analog voltages.

4321out 125.025.05.0 VVVVV

Averaging Amplifier Averaging amplifier – A summing amplifier that

provides an output proportional to the average of the input voltages.

3321

out

VVVV

Difference Amplifier Difference amplifier – A summing amplifier

that provides an output proportional to the difference between two input voltages. Also called a subtractor.

)( 121

3out VV

R

RV

Instrumentation Amplifiers Instrumentation amplifier – A circuit used to

amplify low-level signals in process control and measurement applications.

GCL R

RA

21

Audio Amplifier Audio amplifier – The final audio stage in

communications receivers, used to drive the speakers.

Thank You

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