Operational Amplifiers

Amplifier

Devices used for signal processing

Amplifier

Performs AMPLIFICATION to increase the magnitude of voltage

Amplifier

Other functions include signal inversion, differentiation, integration, addition, subtraction, and comparison

Amplifier

Generally, we model an ___ as a two-port device, with an input and output voltage referenced to ground

Amplifier

defines the factor by which the voltage is changed

Input Impedance

Defined as the ratio of the input voltage and current

Operational Amplifiers

Also referred to as OP AMP

op amp

aka operational amplifiers

op amp

low-cost and versatile integrated circuit consisting of many internal transistors, resistors, and capacitors manufactured into a single chip of silicon

differential input

Ideal Op Amp has a ___, single output amplifier that is assumed to have infinite gain

inverting input, noninverting input

The two inputs are called the ___, labeled with a minus sign, and the ___, labeled with a plus sign.

minus, plus

The two inputs are called the inverting input, labeled with a ___ sign, and the noninverting input, labeled with a ___ sign.

feedback

Op amps usually includes a ___ from the output going to the inverting (closed loop configuration) input to stabilize the amplifier and control of gain

\- it has infinite impedance at both inputs

\- it has infinite gain

\- it has zero output impedance

Golden rules on op amps

Inverting Amplifiers

Constructed by connecting two external resistors to an op amp

Inverting Amplifiers

Circuit inverts and amplifies the input voltage

Inverting Amplifiers

Feedback loop always goes from the output to the inverting input of the op amp, implying negative feedback.

Inverting Amplifiers

Inverting Amplifiers

Inverting Amplifiers

Non-inverting Amplifiers

Circuit amplifies the input voltage without inverting the signal

Non-inverting Amplifiers

Non-inverting Amplifiers

Summer Amplifiers

Circuit adds the input signals

Summer Amplifiers

Output is the negative sum of the inputs

Summer Amplifiers

Summer Amplifiers

Difference Amplifier

Difference Amplifier

Instrumentation Amplifier

Has a very high input impedance

Instrumentation Amplifier

Capability to amplify low-level signals in a noisy environment, often a requirement in differential-output sensor signal-conditioning applications

Instrumentation Amplifier

Consistent bandwidth over a large range of gains

Instrumentation Amplifier

Has large common mode rejection ratio (CMRR). The CMRR is the ratio of the difference mode gain to the common mode gain.

common mode rejection ratio

aka CMRR

CMRR

the ratio of the difference mode gain to the common mode gain

Instrumentation Amplifier

Instrumentation Amplifier

Comparator

Circuit is used to determine whether one signal is greater than another

Comparator

an example of an op amp circuit where there is no negative feedback and the circuit exhibits infinite gain

Comparator

Output is saturated, where it remains at its most positive or most negative value

Comparator

The positive saturation value is slightly less than the positive supply voltage, and the negative saturation value is slightly greater than the negative supply voltage.

Real Op Amps

aka Non-ideal amps

Real Op Amps

have a very high input impedance, so very little current is drawn at the inputs.

Real Op Amps

There is very little voltage difference between the input terminals.

not infinite, magnitude

However, input impedance of a real op amp is ___, and its ___ is an important terminal characteristic of the op amp.

gain bandwidth product

aka GBP