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B - Diodes And Semicon > 4.1 Semiconductions - Integrated Circuits (2) > Flashcards

4.1 Semiconductions - Integrated Circuits (2) Flashcards

1
Q

what is input offset current?

A

the difference between both input currents at an output potential of zero volts

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2
Q

how does input offset current occur?

A

as a result of asymmetry of the two input terminals

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3
Q

how is it possible to balance the asymmetry of the input stages?

A

by the means of offset voltage compensation

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4
Q

what is input bias current?

A

the median value of both of the input bias currents of the op

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5
Q

what is max voltage range?

A

the voltage range which destroys the amp when applied to either input terminals

max +/- 10v

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6
Q

what is the differential input voltage range?

A

the value of the difference between the two input voltages

max +/- 5v

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7
Q

in max voltage range, how can amps be protected from exceeding their limits?

A

protective circuits

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8
Q

how is an op prevented from excessive oscillation?

A

it is frequency compensated by using external or internal circuitry,
Influencing frequency response in order for it to remain stable
whilst decreasing its range

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9
Q

what two types of input impedances occur in the input stages of op amp?

A

differential mode impedance and
common-node impedance

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10
Q

where is output impedance effective?

A

at the output terminal of an op operating in an open loop mode

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11
Q

at what frequency is output impedance?

A

over 100 Htz

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12
Q

in the influence of supply voltage, what is the result of pole reversal?

A

destruction of the op

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13
Q

in the influence of supply voltage, using a stabilised power supply has the tendency to vibrate at a frequency higher than the usual operating range of an op, what is done to compensate for this?

A

capacitors are used to block the voltages of the power supply, directly from the op to ground

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14
Q

in the influence of supply voltage, what must be done if several ops are supplied with voltages from a common source?

A

important to block each and every op to keep individual amps from influencing each other

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15
Q

what is the closed loop voltage gain of a voltage follower circuit?

A

1/unity

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16
Q

what is a summing amplifier used for?

A

to combine the voltages present on two or more inputs into a signal output voltage.

output voltage is proportional to the sum of input voltages

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17
Q

what is the name of the summing amp if the input resistors are all the same value?

A

unity gain inverting adder

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18
Q

what is the name of the summing amp if the input resistors are different values?

A

a scaling summing amplifier

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19
Q

what is an op amp comparator?

A

compares one analogue voltage with another analogue voltage level, or a preset reference voltage and produces an output signal based on the voltage comparison

compares the magnitude of the voltages and determines which is the largest

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20
Q

what type of feedback do op amp comparators use?

A

positive feedback or none at all

21
Q

in op amp comparators, due to its high open loop gain, what does the op do?

A

it either swings fully positive or negative, on the application of varying input signal which passes some preset threshold

Vin greater than Vref then Vout= Vcc+
Vin Less than Vref then Vout = Vcc-

22
Q

in op amp comparator, what is the output voltage totally dependant on?

A

the power supply voltage

23
Q

in op amp comparator, what is used to set Vref? (4)

A

-resistive voltage divider
-battery source,
-zener diode or
-potentiometer (for variable)

24
Q

what are op amps designed and optimised for?

A

used in closed-loop with negative feedback from its output to its inverting input

linear operation

25
Q

what does high gain of a voltage comparator allow it to do?

A

operate non-linearly allowing for heavy saturation

26
Q

a voltage comparator is optimised for continuous saturation, where is it always intended to be?

A

close to one supply rail or the other, not inbetween

27
Q

what can voltage comparators convert?

A

convert linear input signals into digital output,

28
Q

where are voltages comparators commonly used to connect?

A

connect two dissimilar electrical signals with a different supply voltage or reference voltage

29
Q

in voltage comparator, if the output switch is HIGH, what occurs?

A

it creates a high impedance path meaning no current can flow

30
Q

in voltage comparator, if the output switch is LOW, what occurs?

A

creates low impedance path to ground, through the pull-up resistor, with output being pulled to the lower power supply

31
Q

in differential amplifiers, two input voltages are used to calculate and amplify the ‘difference’ of the voltages, what is the circuit sometimes known as?

A

subtractor circuit

32
Q

in differential amplifiers, if the resistors are of equal value, what will the circuit become?

A

unity gain differential amplifier

33
Q

in differential amplifiers, if the resistors are of equal value, what will the voltage gain of the amp be?

A

exactly 1 or unity

34
Q

in differential amps, if V2 is higher than V1, what is the output voltage sum?

A

positive

35
Q

in differential amps, if V1 is higher than V2, what is the output voltage sum?

A

negative

36
Q

in differential amps, what is the method called where the addition of extra resistors to the circuit in parallel are used, used to either add or subtract the applied voltages?

A

Wheatstone bridge

37
Q

if you were to change the resistive elements of a feedback amplifier with capacitive elements, what type of circuit would be created?

A

integrator amplifier

38
Q

what does an integrator amplifier do?

A

causes the output to respond to changes in input voltage, and produces an output voltage proportional to the integral of the input voltage

39
Q

how does an integrator amplifier work?

A

-uncharged capacitor acts like a short circuit allowing current to flow via a resistor.
-capacitor begins to charge due to input voltage
-negative feedback forces the op amp to produce an output voltage that maintains virtual earth at inverting input

40
Q

what does the rate at which a capacitor charges depend on?

A

the value of the resistor or capacitor (RC time constant)

41
Q

in an integrator amp, if you were to apply a square wave input, what would occur?

A

sawtooth wave output
due to capacitor charging and discharging

42
Q

how are differentiator and integrator amp different?

A

the position of the capacitor and resistor has been reversed.

resistor forms part of negative feedback

43
Q

what is a differentiator amp role?

A

produce a voltage output which is directly proportional to the input voltage’s rate of change with respect to time

44
Q

how does a differentiator amp work?

A

-input signal applied to the capacitor. Dc blocked, AC allowed
-frequency dependant

low frequency = high reactance
= low gain
= low output voltage

high frequency = low reactance
= high gain
= high output voltage

45
Q

what is the disadvantages of differentiator amps?

A

-becomes unstable due to oscillation at high frequencies

(prevented by adding a small value capacitor across the feedback resistor)

-capacitive input susceptible to random noise signals

46
Q

in differentiator amps, what are the resulting output signal waveforms from the following?

Square wave
triangular
sine

A

Square wave = spikes
triangular = rectangular
sine = cosine

47
Q

how is control achieved?

A

by comparing the required output with a fixed voltage reference.

48
Q

in control, what can a large loop gain achieve?

A

rapid detection of very small changes in output voltage

B - Diodes And Semicon (14 decks)

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