Elect 2 test 2
This class of amplifier has only one transistor, and amplifies 360° of the input wave.
Class A
This class of amplifier is the simplest to build, but is very inefficient.
Class A
This class of amplifier has two transistors, each of which amplifies somewhere between 180° and 360° of the input wave.
Class AB
This class of amplifier has two transistors, each of which amplifies 180° of the input wave.
Class B
This class of amplifier has one transistor that amplifies less than 180° of the input wave.
Class C
Which class of amplifier uses a parallel resonant circuit to "tune" the amplified frequencies?
Class C
This class of amplifier is very efficient and is often used in mobile phones and home theater systems.
Class D
Which class of amplifier requires an external modulating square wave of a higher frequency than the signal being amplified?
Class D
Which class of amplifier uses a push-pull switching amplifier?
Class D
CMRR stands for
Common mode rejection ratio
A Class B amplifier is a tuned amplifier that is mostly used with RF circuits used in radios and communications.
False
A linear integrated circuit is a digital circuit where many transistors, diodes, resistors and capacitors are fabricated on a single chip of semiconductor material.
False
A push-pull amplifier configuration used in Class B amplifiers is identical to the push-pull switching amplifier used in Class D amplifiers.
False
A typical op-amp consists of two transistors.
False
Acm is the common-mode gain, and for a good amplifier, it should be as large as possible.
False
An ideal op-amp has an infinite output resistance.
False
An op-amp with one input grounded is operating in differential mode.
False
Av(d) refers to the undesirable gain of noise.
False
Class A amplifiers are popular due to the fact that they are efficient and do not require heat sinking.
False
Class AB amplifiers are less efficient than Class A amplifiers, but they have less distortion.
False
Common mode condition of an op-amp occurs when neither input is grounded.
False
Efficiency is very important in early-stage small-signal amplifiers.
False
In an op-amp circuit, the output voltage can be -18 V, even if the op-amp's voltage sources are +15 V and -15 V.
False
It is desirable for an op-amp's common-mode gain Acm to be as large as possible.
False
Most op-amps are assembled from discrete components.
False
Op-Amps are only used to amplify dc signals.
False
Op-Amps that are used as comparators have negative feedback.
False
Power amplifiers are usually used in early amplifier stages, for example to increase the amplitude of an antenna signal.
False
The voltage gain of the op-amp itself, not the op-amp circuit, is referred to as the closed-loop gain.
False
When an op-amp is used without negative feedback as a comparator, it is usually correct to assume that the voltages at the inverting and noninverting inputs are the same.
False
In a Class D amplifier, a square wave is produced from a modulating wave and the input sine wave. What will this square wave look like?
It will have wider pulses when the input sine wave is large, but narrow pulses when the input sine wave is small
What type of transistors are used in a Class D push-pull switching amplifier?
MOSFET
If you have an application where the input voltage is noisy or changes very slowly, you may need to use this type of comparator.
Schmitt trigger
A comparator with built-in hysteresis can be referred to as a
Schmitt trigger.
A Class A amplifier is normally no more than 25% efficient.
True
A problem with Class B amplifiers is that they tend to have more distortion.
True
An ideal op-amp has an infinite input resistance.
True
An ideal op-amp has infinite input impedance, zero output impedance, and infinite voltage gain.
True
An op-amp circuit with a CMRR of 100 dB is doing a better job of rejecting noise than one with a CMRR of 90 dB.
True
An op-amp requires both a positive and a negative voltage source.
True
An op-amp that is behaving as a comparator does not use negative feedback.
True
An op-amp with one input grounded is operating in single-ended mode.
True
Both Class B and Class AB amplifiers require a push-pull configuration.
True
Comparators can be used with both dc and ac inputs.
True
Each amplifier that a signal passes through is called a stage.
True
For a Class B power amplifier, two separate amplifiers are used, one for the positive side of the wave and one for the negative side.
True
If the input voltage to this circuit is positive, the output voltage will be negative.
True
In a Class D amplifier, the modulating wave must be of greater frequency than the wave being amplified.
True
In a push-pull switching amplifier such as one used in a Class D amplifier, one MOSFET is always on, but both are never on at the same time.
True
In a summing amplifier, the current flowing through the feedback resistor is equal to the sum of the currents flowing through the input resistors.
True
It is desirable for an op-amp's differential gain Av(d) to be as large as possible.
True
Most op-amps are built on integrated circuits (chips).
True
The output of a summing amplifier is limited by the value of -Vmax.
True
The voltage gain of the entire op-amp circuit is referred to as the closed-loop gain.
True
To add output bounding to a comparator circuit, Zener diodes are often used.
True
When an op-amp is working as a comparator without negative feedback, the output is almost always driven into saturation.
True
While we often approximate the voltage into an op-amp (Vin) to be 0 V, in actuality it is a very small voltage.
True
With power amplifiers, it is important for the resistance of the load to be nearly equal to the Thevenin resistance of the amplifier.
True
For the best response, how do we want our load impedance (ZL) to compare with our output impedance (Zout)?
ZL should be much, much larger than Zout
For the best response, how do we want our source impedance (Zs) to compare with our input impedance (Zin)?
Zs should be much, much smaller than Zin
A linear integrated circuit is this type of circuit:
analog
On a power transistor, the case or housing of the transistor is usually connected to the
collector
A circuit built from individual transistors, diodes, and resistors is said to be constructed from _________ components.
discrete
In a comparator circuit, when there is a higher reference voltage required for the output voltage to switch high and a lower reference voltage required for the output voltage to switch low, the system is using ____________.
hysteresis
When the load resistance is not close to the Thevenin resistance of the amplifier, the amplifier will be very inefficient. This is not important for small-signal amplifiers, but for power amplifiers it means that there will be a great deal of heat loss. There are steps that can be taken that will make the load resistance and the Thevenin resistance more equal. These steps are known as
impedance matching
We want to build an op-amp circuit that has a closed-loop voltage gain of -5.5. What type of amplifier circuit should we build?
inverting amplifier
The op-amp input with the negative sign is called the
inverting input
An op-amp is the most common
linear integrated circuit
The part of a Class D amplifier that converts the amplified square wave back to a sine wave is the
low-pass filter
Common-mode signals generally refer to
noise
Common-mode rejection occurs in a differential amplifier when
noise appears on both inputs and is not amplified
We want to build an op-amp circuit that has a closed-loop voltage gain of 12. What type of amplifier circuit should we build?
noninverting amplifier
The op-amp input with the positive sign is called the
noninverting input
In the pulse-width modulator part of a Class D amplifier, what is used to create the square wave from the input and modulated waves?
op-amp comparator
A configuration where two amplifiers are used, each amplifying half of the time, is called
push-pull
Which of the following is not part of a Class D amplifier?
tank circuit
The output of an op-amp with a double-ended input is equal to the amplification of
the difference between the inputs
The output voltage of a comparator is most dependent on
the power supply voltages
A voltage follower circuit can also be called
unity follower
If the same op-amp is used, which of the following circuits will have the greatest input resistance?
voltage follower
We want to build an op-amp circuit that does not change the voltage level but provides a maximum input impedance and a minimum output impedance. What type of amplifier circuit should we build?
voltage follower
When the two inputs of an op-amp operating in the differential mode are equal, the output will be
zero
