Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ELEC2130 - Circuit Design > Detection circuits > Flashcards

Detection circuits Flashcards

1
Q

What is the grounded version of a currten-to-voltage converter?

A

[Picture32]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the supply version of a currten-to-voltage converter?

A

[Picture33]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the equation for the grounded current-to-voltage converter?

A

Vout = RFeedback × ID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the equation for the supply current-to-voltage converter?

A

Vout = -RFeedback × ID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why are op-amps a good way of converting current to voltage?

A

Because of the virtual ground principle, they can provide a low impedance to ground

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is often put in parallel with Rfeedback?

A

A capacitor to improve stability (by reducing the grain at higher frequencies)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a comparator?

A
  • This allows us to detect when an input signal has crossed an arbitrary threshold (effectively a 1-bit ADC).
  • Vin > Ref : Output will be low
  • Vin < Ref : Output will be high
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are 4 problems with a comparator circuit?

A

> If the input changes slowly then the output will not change abruptly as the op-amp may be operating in its linear region

> Any noise on the signal will cause multiple transitions at the output during the time that the signal is crossing.

> If the output is saturated near the power rails, then this is unlikely to be convenient for the connected microcontroller.

> Op-amps tend to have a limited input range which may limit the size of the input signal.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is better than a comparator?

A

A dedicated IC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the tropology of a schmitt trigger?

A

[Picture34]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the operation of the schmitt trigger?

A

The solution to the problem of noise on the signal causing multiple transitions at the output during the time that the signal is crossing a threshold is to have a threshold that changes after a transition has been made. This creates an upper and lower threshold.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What the circuit for an active half-wave rectifier?

A

[Picture35]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

For an active half-wave rectifier what happens when:

a) Vin > GND
b) Vin < GND

A

a) Vin > GND

> The op-amp will rise until V+ = V-

> The output is unity gain

b) Vin < GND

> The diode is reverse biased so the output is 0V

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the issue with active half wave rectifiers?

A

Works well for low frequencies (< Few KHz) but at higher frequencies (> 100kHz) the output becomes distorted. This problem can be negated using clamped feedback:

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What the circuit for an active half-wave rectifier with clamped feedback?

A

[Picture37]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

For an active half wave rectifier with clamped feedback what happens when:

a) Vin > GND
b) Vin < GND

A

a) Vin > GND

> D1 is reverse biased

> D2 is forward biased

> Vout = 0

b) Vin < GND

> D1 is forward biased

> D2 is reverse biased

> Forms an inverting amplifier and so the output = Vin

17
Q

What is the circuit for an envelope peak detector?

A

[Picture38]

18
Q

How does an envelope peak detector work?

A

> The capacitor will charge up to VC = Vpeak - Vd

> Capacitor needs to be discharged before detecting a new peak.

19
Q

What is the circuit for an active peak detector?

A

[Picture39]

20
Q

How does an active peak detector work?

A

> The capacitor will charge up to VC = Vpeak

> Capacitor needs to be discharged before detecting a new peak.

21
Q

What is the circuit for an active peak detector with clamped feedback?

A

[Picture40]

22
Q

What is an analogue signal?

A

A signal represented by a continuous quantity.

23
Q

What is a digital signal?

A

A signal represented by a discrete quantity with a finite possible set of values.

24
Q

How does digital representation of analogue signals work?

A

By sampling a signal many times per second and assigning the amplitude at that point a voltage level. Each voltage level is represented by a binary number.

25
Q

Define ‘quantisation’

A

> The process of assigning the voltage amplitude of an input signal to a discrete voltage level during sampling.

> There is only a fixed number of voltage levels so the input signal is assigned to the closest one.

26
Q

Define ‘FSV’

A

Full Scale Value (FSV): The value that corresponds to the highest quantisation voltage level

27
Q

Define ‘FSR’

A

Full Scale Range (FSR): The difference between the highest and lowest quantisation voltage level.

28
Q

Define ‘Resolution’

A

The number of different quantisation levels that we have

29
Q

Define ‘Effective Resolution’

A

The number of different quantisation levels that an input signal spans.

30
Q

Define ‘Interval’

A

The difference in voltage between each voltage level

31
Q

What are the number of levels for n bits?

A

Levels = 2n

32
Q

What is the equation for resolution %?

A

Resolution% = 100 × (1 / 2n)

33
Q

What is the equation to calculate the interval voltage?

A

Interval = FSR / (2n - 1)

34
Q

What is the equation to calculate the quantisation error?

A

Quantisation err = 1 / 2 × FSR / (2n - 1)

35
Q

What are the constraints/considerations when using an ADC for a microcontroller?

A

> ADCs are always positive so FSR = FSV

> You cannot apply a negative input to the ADC

> Maximum input value is determined by an internal voltage reference which determines FSV

36
Q

What are diode clamps?

A

They are used to keep input voltages within the permitted input range.

37
Q

How are diode clamps applied?

A

[Picture 41] > Such that if the input voltage goes outside the desired range, then the diodes will short and bring the input within the correct voltages

38
Q

For diode clamping in this example, what happens when:

a) Vin > Vsupply
b) Vin < GND

A

a) Vin > Vsupply :

> Top diode is forward biased and so the input is limited to the supply voltage.

> Bottom diode is reverse biased.

b) Vin < GND :

> Bottom diode is forward biased and so the input is limited to GND.

> Top diode is reverse biased.

ELEC2130 - Circuit Design (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions