Operational amplifier fundamentals (Test 15)
Practical op amps have an input impedance of
1 Mohms
In voltage followers, what percentage of the output is feed back to the input
100%
Which of the following is true of the noninverting summer?
All inputs are combined and then amplified
The inverting summing amplifier performs which function?
All of the above
The output of the noninverting amplifier
All of the above
Which statement about difference amplifiers is true?
All of the above
When configured for a gain of one, the non-inverting summing amplifier acts as
An averager
Voltage follower circuits are used
As buffer circuits
The summing junction of the inverting summer is
At virtual ground
What is another name for the voltage follower?
Both a. and b.
In a typical difference amplifier, signals are applied to which input?
Both inputs; neither are grounded
The gain of the noninverting amplifier
Can not be less than one
The output of a noninverting summing amplifier
Can not exceed the negative supply voltage
An unwanted signal present at both inputs of the difference amplifier is the
Common-mode input voltage
An op amp configured as an open-loop comparator
Compares a voltage with a reference
The purpose of hypothesis in an op amp comparator circuit is to
Decrease input sensitivity
If the feedback resistor of a noninverting amplifier is decreased, the gain
Decreases
In the inverting summing amplifier, feedback current is
Equal to the sum of the input currents
The gain-bandwidth product of the voltage follower is
Equal to the value in the specification sheets
To change a difference amplifier to an inverting summer
Ground the noninverting input
A fractional gain amplifier
Has an output magnitude that is less than the input magnitude
Inverting summing ampifiers
Have two or more inputs
Ideally, the voltage follower should have
High input and low output impedance
One advantage of the unity-gain amplifier over the gain-of-one amplifier is
Higher input impedance
If the value of an inverting amplifier input resistor were lowered, calculated gain would
Increase
The different operating modes of the inverting summing amplifier depend upon the
Input and feedback resistor values
Input bias current enters
Into both inputs of an op amp
The output of the inverting summer
Is a function of the combined input signals
Which of the following is not true of an inverting amplifier?
Is has low input impedance
You can eliminate output-offset voltage by
Offset nulling the device
In a sine wave to square wave inverter, threshold voltage is determined by:
Positive feedback
The closed-loop op amp configuration
Provides stability
For a typical difference amplifier. the polarity of the output depends upon the
Relationship of the noninverting input voltage to the inverting input voltage
Which operation is not possible for the noninverting summing amplifier
Scaling
The main feature of the difference amplifier is its ability to
Subtract and amplify two voltages
The point where two or more voltages or currents meet and combine is the
Summing point
When the input resistor of an inverting summer are equal to RF, Vo equals
The negative sum of the input voltages
The breakpoint frequency occurs when
The output voltage drops 3dB from the starting voltage
Each input of the inverting summing amplifier is multiplied by
The ratio of RF to the corresponding RIN
Which op amp constraints apply to the noninverting summer?
They all apply
Which statement about comparator circuits is false?
They can never saturate in the closed-loop form
The output of a difference amplifier is V2-V1. If the input signal are opposite in phase but equal in magnitude, the circuit output is
Twice the magnitude of the input signals and in phase with the *noninverting* input signal
Differential voltage is the voltage measured at the
Two input terminals
In a comparator circuit, a reference voltage is
Used as a trigger voltage
Slew rate is measured in
Volts per microsecond
In an inverting op amp configuration, the noninverting terminal is connected to the
circuit common
To increase the bandwidth of the inverting amplifier, decrease the
circuit gain
From the top view of a DIP, pin count is
counterclockwise
In the noninverting summing configuration, the inverting input is connected to
ground
Voltage comparators are typically used as
level detectors
