Revision Deck Flashcards
What is the notation you need to remember for small signal analysis?
BJT: How should you connect a external voltage source to the EB junction of a transistor to enable forward bias?
You want to connect the positive terminal (high voltage) to the p-side and the negative terminal to the n-side. This goes for both npn and pnp.
If there is no resistor connected to the emitter, what small signal model should you be using?
hybrid-pi
What is the method of determining the gain of a CE amplifier that you need to remember
Steps are as follows:
Vsig -> ib by multiplying by 1/(Rsig + rin)
ib -> ic by multiplying by β
ic -> vo by multiplying by Rc
where Rc is the resistance in parallel with vo
Why are two different definitions for the gain, i.e. Av and Avo used to characterise amplifiers?
It is just convention to make it easier to deal with circuits when they get more complex
When you want to see how Rsig loads the device on its own, or how RL loads the device.
MOSFET: CS amplifier small signal model, Rin, Ro, Av, Gv ?
Av =Vo /Vi
Gv =Vo/Vsig
MOSFET: CS amplifier with source resistance, small signal model, Rin, Ro, Av, Gv
𝐴vo = 𝑔𝑚𝑅𝐷 / (1 + 𝑔𝑚𝑅s)
Gv = 𝑔𝑚𝑅𝐷 / (1 + 𝑔𝑚𝑅s)
MOSFET: CG amplifier small signal model, Rin, Ro, Av, Gv
MOSFET: CD amplifier (source follolwer) small signal model, Rin, Ro, Av, Gv
Look at the t-model it is just potential division.
What do you need to remember about this thevenin question?
You need to do successive thevinin equivalent circuits.
How do you apply Nortons Theorem?
Norton’s theorem is used to represent a part of network by a current source In and a parallel impedance Zn .
To determine In, short-circuit the two terminals of Network A and measure the current.
To determine Zn , reduce all external (i.e., independent) sources in Network A to zero by short-circuiting voltage sources and open-circuiting current sources. Then obtain the input impedance of Network A, Zn .
Single-time-constant circuits
Single-time-constant (STC) circuits are those circuits that are composed of or can be reduced to one reactive component (inductance or capacitance) and one resistance.
𝜏 = 𝐿 / 𝑅
or
𝜏 = 𝐶𝑅
time constant of the circuit
Where does the maximum error comes from in the magnitude-response and phase-response plots for High Pass and Low Pass?
it comes from approximating two straight-line asymptotes (one of which is the slope).
For both High Pass and Low Pass the maximum error in the mangitude-response graphs is 3db
Similarly the maximum error in the phase response graphs is 5.7°
Sketching Magnitude Response
What sort of function is this?
First-order function of a LP
What sort of function is this?
What is a pole and what is a zero?
Poles are the coefficients associated to s-values in the denominator.
Zeros are coefficients associated to s-values in the numerator.
A pole at s=a (a≠0) leads to a slope of what…
-45º/decade
and extends from 0.1|a| to 10|a|.
Remember that slope starts 0.1 before the pole value and finishes 10x after.
Quickly determining the pole frequencies of CE amplifier?
Last one
Upper 3-dB frequency equation
i.e. the frequency of the dominant pole (if it exists…)
What happens if it doesn’t exist?
tauH will equal the sum of tau’s multiplied by 2π
In a CS Amplifier, do capacitors contribute poles or zeros?
poles
How can you better estimate the 3-dB frequency even if the poles are far apart?
What is the miller approximation?
What about millers theorem
Miller’s approximation is using the dominant pole to determine the 3dB frequency fH.
The dominant pole is due to the capacitance at the input side.
Millers theorem, you take into account the effects of poles the 3dB frequency on the input and output side.
Oscillators: What is the Barkhausen Criterion?
Negative Feedback: What are the benefits of negative feedback?
- Desensitize the gain. Gain is less sensitive to variations in values of circuit components.
- Reduce nonlinear distortion. Keep output as linear as possible with respect to the input.
- Reduce the effect of noise. Minimize the contribution from unwanted noise sources.
- Control the input and output resistances. Raise or lower the input and output resistances by the selection of an appropriate feedback topology.
- Extend the bandwidth of the amplifier.
Negative Feedback: desensitivity factor
The percentage change in Af is smaller than the percentage change in A by a factor equal to the amount of feedback.
This factor is called the desensitivity factor, 1+Aβ
Negative Feedback: What is the value of the feedback gain (β) for this ideal non-inverting amplifier?
Negative Feedback: What is the Series – Shunt configuration used for?
When the output is a voltage source (RHS)
Negative Feedback: What is the Series – Series configuration used for?
When the output is a current source (RHS)
Negative Feedback: Configuration equations for Gain, Rin and Rout.
Power Amplifiers: What determines the Power Amplifier classification
Classification depends on the placement of the Q-point (DC operating point).
Power Amplifiers: What determines the conduction angle of Power Amplifiers
The Q-point (DC operating point).
Oscillators: Phase-shift oscillator Transfer Function
Power Amplifiers: Class AB
Power Amplifiers: What is the symbol for average load power?
And total average supply power?
PL
PS
