Operational Amplifiers Flashcards
How is an Op-Amp coupled ?
DC coupled
What is direct coupling or conductive coupling or DC coupling ?
Transfer or electrical energy
How is electrical energy transfered in DC coupling ?
Via physical contact through a conducting medium
What are the other methods of coupling electrical cicuits ?
Inductive and Capacitive circuits
How is the low frequency response of direct coupling ?
Very good.
How good is the low frequency response of direct coupling ?
It passes the full spectrum along with DC (0 Hz)
Why is DC coupling used as default in IC Op Amps ?
Difficult to fabricate large coupling capacitors on chip
What is the gain of an Op Amp like ?
High gain
What kind of electronic amplifier is an Op Amp (V or I) ?
Voltage
Why is it that the characteristics of an Op Amp are dependent on the external components and not on temperature coefficients and the manufacturing process ?
Negative feedback
What are some examples of differential amplifier (apart from Op-Amp) ?
Fully Differential Amplifier
Instrumentation Amplifier
Isolation Amplifier
Negative Feedback Amplifer
What is a fully differential amplifier ?
Like an op amp, with 2 outputs
What is an instrumentation amplifier ?
Uses 3 op amps
What is an isolation amplifier ?
Similar to an instrumentation amplifier, but with greater tolerance to common mode voltages
What is negative feedback amplifier ?
Built from one or more op amps, + resistive feedback network
How is open loop gain measured ?
In the absence of feedback network from output to input
How is gain measured, in general ?
Output / Input voltage
What is the open loop gain of an ideal op amp ?
Infinite
What is the input impedance of an ideal op amp ?
Infinite input impedance
What is a consequence of infinite input impedance ?
Zero input current
What is the bandwidth of an ideal op amp ?
Infinite
What is the phase shift of an ideal op amp ?
Zero phase shift
What is phase shift ?
Phase difference in between two or more quantities (waves)
What is the slew rate of an ideal op amp ?
Infinite
What is slew rate ?
Maximum rate of change of output voltage per unit time
What is the CMRR of an ideal op amp ?
Infinite
What is the PSRR of an ideal op amp ?
Infinite
Why are closed loop amplifiers prefered over open loop amplifiers ?
Open loop gain is not well controlled by the manufacturing process
What is a voltage follower ?
A buffer. (Gain of 1)
What are filters ?
Remove unwanted signals during signal processing
What kind of filters do op amps find application in ?
Active filters
Why are active filters called active ?
They contain active components like amplifiers or FETs
What is the disadvantage of a passive filter ?
Amplitude of the output is always less than the input
How do the active components in an active filter amplify the output signal ?
By drawing energy from an external source
What is a low pass or high cut filter ?
Passes signals with frequency lower than cutoff
What is a high pass or low cut filter ?
Passes signals with frequency higher than cutoff
What is a band pass filter ?
Passes frequencies in a range and rejects outside the range
When are isolation amplifiers used ?
Applications where electrical insulation in between source and output is desired
What is an application of an isolation amplifier ?
Medical instrumentation
Source - Sensor
Target - Patient
What is the order of a filter ?
Number of RC poles used in the filter
