ECD II PresentationOP-AMP Applications

• Presented by Group 12

• Aroosa• Sheher• Sidra Ali

Introduction

What is OP-AMP

Mathematics of OP-AMP

Characteristics of OP-AMP

Ideal OP-AMP

Types of OP-AMP

Applications of OP-AMP

Description of OP-AMP applications

What is Op Amp

• An Operational Amplifier (Op-Amp) is an integrated circuit that uses external voltage to amplify the input through a very high gain

What an Op-Amp lookslike to a lay-person

What is an Op-Amp? – The Surface• .

• What an Op-Amp lookslike to an engineer

What is an Op-Amp? – The Inside• The actual count varies, but an Op-Amp contains

several Transistors, Resistors, and a few Capacitors and Diodes.

• For simplicity, an Op-Amp is often depicted as this:

Inverting

Input

Non-

Inverting

Input

Positive

Power

Supply

Negative

Power

Supply

Output

Mathematics of the Op-Amp

• The gain of the Op-Amp itself is calculated as:

G = Vout/(V+ – V-)

• The maximum output is the power supply voltage

• When used in a circuit, the gain of the circuit (as opposed to the op-amp component) is:

Av = Vout/Vin

Op-Amp Characteristics

• Open-loop gain G is typically over 9000

• But closed-loop gain is much smaller

• Rin is very large (MΩ or larger)

•Rout is small (75Ω or smaller)

Ideal Op-Amp Characteristics

Types of Op-Amps

o Inverting

oNon-inverting

oSumming amplifier

oThe voltage follower

o Integrator

oDifferentiator

Applications of Op-Amps

• Comparator

• Integration and differentiation

• Charge amplifier

• Capacitance multiplier

• Oscillators

• Filters

• Audio and video preamplifiers and buffers

Applications of Op-Amps

• Voltage regulator and current regulator

• Digital-to-analog converter

• Voltage clamps

• Oscillators and waveform generators

• Analog computer

Comparator

• Compares two voltages or currents and outputs a digital signal indicating which is larger.

• Two analog input terminals and one Output

.

• The op-amp's output voltage is limited by the supply voltage.

Integration

•Performs the mathematicaloperation of Integration.

• Output signal is determined by the length of time a voltage is present at its input as the current through the feedback loop charges or discharges the capacitor as the required negative feedback occurs through the capacitor.

Differentiation

• Amplifies the difference between two voltages but does not amplify the particular voltages.

=Common-mode gain of the amplifier. =Differential gain

• Used to null out noise or bias-voltages that appear at both inputs, a low common-mode gain is usually desired.

Differential and Common Gain

•

• Differential Gain (Ad):

• Ad = 1/2[R3/(R1+R3)] [(R4 + R2)/R2 + R4/R2]

• Mode Gain (Acm=VOUT/ Vcm)

• Acm = [R3/(R1+R3)] [(R4 + R2)/R2 - R4/R2]

Charge amplifier• Constructed using op-amps with a

feedback capacitor.• The charge amplifier just transfers

the input charge to another reference capacitor and produces an output voltage equal to the voltage across the reference capacitor

• The circuit acts as a charge-to-voltage converter.

• The input impedance of the circuit is almost zero

Capacitance Multiplier

• Uses an amplifier to make a capacitor function like a capacitor that is much large.

• Used as a capacitance multiplier in such a way that multiple small physical capacitances are combined in the integrated circuit technology to yield a large overall capacitance.

• The aim is often to multiply the original capacitance value hundreds and thousands of times.

Oscillators

• Produces a repetitive, oscillating electronic signal, often a sine wave or a square wave.

• convert direct current (DC) from a power supply to an alternating current signal.

• It contains an energy-storing element (a capacitor or, more rarely, an inductor)

Active FILTERS

• Types:

• Low pass filter

• High pass filter

• Band pass filter

• Band reject filter

Active Filters• A filter contains a device like an Op Amp

• LP allow low frequencies HP allow high frequencies

• Cut of frequency :a cutoff frequency is a frequency level

above or below where a device fails to operate.

R2

+

-

+

V0

__

+ Vcc

- Vcc

-

+

R1

C

Low pass filter

Low pass filter transfer

function

Low pass filter Cutoff

frequency

Low Pass Filter

• Passes low frequency signals with amplification and gain control

Active Low Pass Filter with Amplification• the amplitude of the output is increased by the pass band

gain, AF of the amplifier.

Frequency Response Curve

High Pass Filter

• Passes high frequency signals with amplification and gain control

First Order Active High Pass Filter with 1 Gain

Active Band Pass Filter

• Frequency selective filter circuit

• Range is set between two cut-off frequency points “lower frequency” ( ƒL ) and the “higher frequency” ( ƒH ) while attenuating any signals outside of these two points.

• Made by cascading together a single Low Pass Filter with a single High Pass Filter .

Active Band Pass Filter Circuit

Band reject filter

• Band stop filters reject a specified band of

• frequencies and pass all others.

• The response is opposite to that of a bandpass

Graphical representation