Amplification

Question 1

What is an amplifier

Answer 1

Increases the magnitude of signals so they can be processed, displayed or recorded

Question 2

Measurement system, typically includes?

Answer 2

• Transducer
• Amplifier
• Display or recording device

Question 3

Amplification Definition

Answer 3

The process of increasing the magnitude of a signal

Question 4

Gain Definition

Answer 4

The ratio of output voltage to input voltage

Question 5

Sensitivity Definition

Answer 5

Output per unit input for a transducer

Question 6

Feedback definition

Answer 6

A portion of the output returned to the input. Can be positive or negative

Question 7

Differential amplifier definition

Answer 7

Measures the voltage difference between two inputs

Question 8

Common mode signal definition

Answer 8

A signal that appears equally on both amplifier inputs

Question 9

Common Mode Rejection Ratio Definition

Answer 9

A measure of how well an amplifier rejects common mode signals relative to differential signals

Question 10

Gain Equation

Answer 10

Output Voltage / Input Voltage

Question 11

What performance does sensitivity describe

Answer 11

Transducer performance

Question 12

What is an operational amplifier (op-amp)

Answer 12

An integrated circuit consisting of many transistors. It has:
- Non-inverting input
- Inverting input
- Output terminal
- Positive and negative power supplies

Question 13

Ideal op-amp characteristics

Answer 13

• Infinte input impedance
• Infinite gain
• Zero output impedance

Question 14

Negative Feedback

Answer 14

Stabilises gain and makes amplifiers predictable

Question 15

Positive Feedback

Answer 15

Reinforces the input and is used in comparators, oscillators and switching circuits

Question 16

Inverting amplifier gain equation

Answer 16

-Rf / Ri

Question 17

Inverting amplifier characteristics

Answer 17

• Output polarity is opposite to input
• Gain magnitude set by resistor ratio

Question 18

Non-inverting amplifier gain equation

Answer 18

1 + (Rf / Ri)

Question 19

Non-inverting amplifier characteristics

Answer 19

• Output has same polarity as input
• Higher input impedance than inverting amplifier

Question 20

Differential amplifier use

Answer 20

Used to measure the difference between two input voltages

Question 21

Differential amplifier gain equation

Answer 21

R2 / R1
- when resistor ratios match

Question 22

Common mode signal in an ideal differential amplifier

Answer 22

Common mode voltage = 0 output

Question 23

Common mode signal in a real amplifier

Answer 23

• Some common mode signal leaks through
• Common mode gain

Question 24

CMRR equation

Answer 24

CMRR = Differential gain / common mode gain

Question 25

Larger the CMRR ?

Answer 25

Better noise rejection

Question 26

What is an instrumentation amplifier

Answer 26

A specialised differential amplifier used in medical devices

Question 27

Advantages of an instrumentation amplifier

Answer 27

- Very high input impedance - Very high CMRR - Gain adjustable with a single resistor - Excellent for biopotential measurement