Op-Amps Flashcards
Signal Conditioning has the following Functions:
Amplification
Signal Modification
Impedance Matching
Demodulation
Isolation
Filtering
linearisation
Explain Each of those Concepts
Amplification - Increasing the Magnitude of a Signal
Signal Modification - Alteration to a signal characteristic Such as Amplitude, Phase or Frequency.
Impedance Matching - Where Load Impedance is equal to Internal Impedance / Source Impedance to maximize power transfer and minimise signal reflection
Demodulation - Extraction of the Original signal (information) from a carrier wave
Isolation - preventing a direct electrical connection between two parts of a circuit
FIltering - selectively allowing certain frequencies of an electrical signal to pass through while blocking others.
Linearisation - approximating a nonlinear system by a linear one within a certain operating range. - eg. a system could have limitations at high power, causing distortion, linerisation reduced distortion with approximations of what the output signal should be.
What is Signal Conditioning
Manipulation of an analog signal, to prepare for processing
What is Interfacing
Linking Together of multiple electronic devices.
What is a Passive Circuit
Only uses Components that dont require and external Power Source
eg. resistor,capacitor,inductors
What is an Active Circuit
uses Components that require and external Power Source
rg. Silicion Chips
Derive an Equation that Calculates the Voltage output across R0
Note that R0 needs to be re-calculated if there is a load resistance.
What is an Amplifier
Why are Amplifiers Required
Produces an analog electrical signal that is a function of the input
Passive Circuits will Dicipate Energy, Causing the Final Processed Wave to be Lower in Energy (amplitude)
Amplifiers increase the Energy of the System, to compensate.
Describe the Following Amplifiers
Voltage Amplifier
Current Amplifier
Transconductance Amplifier
Transresistance Amplifier
VA - Outputs Voltage Proportional to its Input Voltage
CA - Outputs Current Proportional to its Input Current
TCA - Outputs Current Proportional to its Input Voltage
TRA - Outputs Voltage Proportional to its Input Current
What are the name of the Following Amplifiers:
Outputs Voltage Proportional to its Input Voltage
Outputs Current Proportional to its Input Current
Outputs Current Proportional to its Input Voltage
Outputs Voltage Proportional to its Input Current
Voltage Amplifier
Current Amplifier
Transconductance Amplifier
Transresistance Amplifier
Explain the Ideal Voltage Amplifier Model
Infinite Input impedance, to minimise energy dissipated in the internal/source resistance.
Zero Output impedance, to Minimise Energy Disiapted on output inside the Amplifier
Both Allow for 0 voltage Looses, and a Perfect Amplification without Distortion.
Draw the ideal voltage amplifier
What does Voltage Gain Equal?
What is the load effect
Explain why it needs to be considered in amplifiers
impact that connecting a load has on the performance of a circuit
ie. connecting a device to a powersupply, will cause a different voltage across the load, then connecting a difference device. this is due to the ratio of internal: External Impedance changing, causing different amounts of voltage to be dissipated in the load.
Impedance of the Input Circuit must be much smaller then the Output impedance circuit (factor of 10) for consistent load voltage across a range of devices.
Impedance of the Input Circuit must be much larger then the Output impedance circuit (factor of 10) for consistent load current across a range of devices.
Impedance of the Input Circuit must equal to the Output impedance circuit (factor of 10) to maximize of power transfer.
1
Name Both Major Op-Amp Limitations
Skew Rate
Gain Bandwidth Product (GBP_
Explain Gain-Bandwidth Product
How do you calculate Gain in DB
Gain is Non-Constant for every frequency
High Frequency Inputs causing major reductions in Gain.
Gain-Bandwith is the linear region where gain is considered constant
Going Beyond said Bandwith (Cut off Frequency) can cause major distortion.
GBP is defined as the product of the Low-Frequency Open Loop Gain & Cut of Frequency.
A0 * Fc
This Value Remains Constant for the same Amplifier
A0 * Fc = A*f
Explain Skew Rate
What occurs at high frequency
the maximum rate of change of an amplifier’s output voltage per unit time
dV/dt can start to become linear, causing a deformed output
Explain Open-Loop Gain
Explain the Ideal Op-Amp’s A0 Value
amplification achieved by an Op-Amps with no feedback applied
Ratio of output voltage to Input voltage when operating in an open loop configuration
A0 value for an ideal op-amp is infinite , from the ideal Op-Amp conditions.
What are Vin1 & Vin2
Vin1 is connected to the inverting terminal
Vin2 is connected to a Non Inverting Terminal
What is the Inverting Terminal
What is the Non-Inverting Terminal
When a signal is applied to the inverting terminal, the op-amp amplifies the signal and inverts its phase by 180 degrees. This means if the input signal is positive, the output will be negative
When a signal is applied to the inverting terminal, the op-amps output signal will be inphase with the input signal. op-amp amplifies the signal without changing its phase
How do you Calculate VOut
Draw the Non-Ideal Open Loop Op-Amp
infinite resistance in
zero resistance out
Why is Neglegable current drawn into the Inverting and Non-Inverting terminals
Both are connected with a resistance that is Ideally infinite, or extremely large in comparison to the source resistance
2
Explain Saturation
Signal Cannot be amplified beyond the Voltage Supplied to the Amplifier (V+ & V-)
Signal is amplified not in proportion
Draw the Following Negative feedback Amplifers
Non-Inverting
Inverting
Buffer
Differential
Explain what each do
Non-Inverting : amplifies the input signal without inverting its phase
Inverting produces an output signal that is inverted, or 180 degrees out of phase
Buffer: Doesnt provide any gain, used to transfer a signal from one part of a circuit to another despite both sources having varing impedances, reduces signal reflection and Power Transfer.
Differential : amplifies the difference between two input voltages while suppressing any voltage common to the two inputs
What is Rin for an Inverting & Non-Inverting Amplifier
Explain Virtual Ground on an Inverting Amplifier
At this point the Potential Difference of the inverting input node is 0, the op-amps adjusts its output to make the voltage difference as close to zero.
Derive Av for a Non-Inverting Op-Amp
Derive Av for an Inverting Op-AMps
Draw the following Amplifiers with Negative Feedback
Non-Inverting
Buffer
Inverting
Differential
Draw a Buffer Amplifier and Derive the Gain
Explain its application using two diagrams
Design two different Circuits ,one using 1 amplifier and the other using two, explain the problem with only using 1 amplifier.
Draw a differential amplifier
Derive the Voltage output for a differential amplifier
Explain 1 potential problem with the differential amplifier
What must the design have to achieve CMRR
Ratio of R2/R1 must be the same as R4/R3
Loading effect of sensors or input circuits affects input impedance
A buffer can be used to negate the loading effect
Explain what problem the Instrumentation Amplifier solves
Draw an Instrumentation amplifier
Derive the gain for an instrumentation amplifier
2 Resistors much be changed in order to alter gain
Instrumentation amplifier only R1 has to be changed
Draw how a Sensor connected to a wheatstone bridge connected to a differential amplifier
Explain 1 limitation
Draw how a Sensor connected to a wheatstone bridge connected to a differential amplifier
Explain 1 limitation
Explain how a Differential amplifier solves the issue of interference from an outside source
