Input from students
Week ending May 17, 2013
1.1 We learned that an AC signal is a voltage or current that changes with time and a DC signal
stays constant with time.
1.2 We learned that electronic circuits contain at least one electronic device, which must be
replaced with an equivalent circuit in order to analyze the full circuit.
1.3 We learned that in order to analyze an AC equivalent circuit, we need to know the DC
characteristics of the circuit.
1.4 We learned that an amplifier can be represented with a dependent source.
1.5 We learned how to find voltage, current and power gains in decibels.
1.6 We learned about the non-linearity of practical amplifiers and the ideal position of the bias
point of an amplifier.
Prof. cooments/input
Very good. Keep up the good work! I can add

A signal can be represented as a function of time (time domain), or in terms of the
frequency components in it (frequency domain).
Week ending May 31, 2013
2.1 We learned that semiconductor diodes are made from p-type and n-type silicon that create a
potential at the junction and that the diffusion and drift currents balance each other out when no
external voltage is applied to the diode.
2.2 We learned that an ideal diode acts as a short circuit when the voltage on the anode is higher
than the voltage on the cathode; this can be used in a half-wave rectifier to eliminate either the
positive or negative parts of an ac voltage. Thus a DC voltage can be generated from an ac
voltage.
2.3.1-2.3.3 We learned that there are several more realistic models for diodes: an ideal diode in
series with a DC source, an ideal diode in series with a DC source and a resistance and a
mathematical model called the exponential model.
2.3.4 We learned that an ac model for a diode is a resistance based on the DC current through the
diode.
2.3.5 We learned that since the voltage across a diode does not change substantially despite large
lange in current through it, the diode can be used to regulate a voltage, i.e. keep the voltage at a
constant level. This leads to use of a diode as a voltage regulator.
2.3.6 We learned that Zener diodes, operating in reverse bias, can sustain a larger DC voltage
than diodes operating in forward bias. Zener diodes are used in commercial voltage regulators.
Very good!
Week ending, June 14, 2013
2.3.7 We learned how to use diodes to clip the output waveform, clamp (add
a DC offset) the output waveform or double the output waveform.
2.4.1 We learned that connecting a capacitor in parallel with the output
resistor of a rectifier circuit creates an envelope detector whose output
remains close to the peak output voltage of a HWR.
2.4.2 We learned about the importance of using a diode that has a larger
reverse breakdown limit than the peak inverse voltage (PIV) in the circuit.
2.4.3 We learned about the two possible configurations of a full wave
rectifier - the center tapped transformer and the bridge rectifier - and
how to calculate the PIV across the diodes in these circuits.
3.1 We learned that a BJT transistor can be viewed as p-type material
sandwiched by n-type material or the inverse; the center material is called
the base while the two sandwiching materials are called the emitter and
collector. KCL must apply, so the current flowing from/to the emitter must
be equal to the current into/from the base plus the collector.
3.2 We learned that the emitter-base junction must be forward biased and
the collector-base junction must be reverse biased for the BJT to be in the
active region of operation; when the collector-base junction is forward
biased, the BJT is in the saturation region.
3.3.1 We reviewed the essential equations: the exponential model for the
collector current and the definitions of alpha and beta (alpha = ic/ie,
beta = ic/ib).
3.3.2 We learned that the I-V characteristic graph for a BJT, with Vbe held
constant, looks like the exponential model in the saturation region, which
occurs first, and then looks linear in the active region.
3.3.3 We learned that the Early voltage is the same regardless of the Vbe.
3.3.4 We learned that the Early voltage can be used to derive a more
accurate expression for the collector current in the active region.
3.4 We learned how to replace a BJT with a common base or common emitter
model for DC analysis and that in the saturation region, Vce = 0.2V and Vbe
= 0.7V.
4.1 We learned that a MOSFET transistor can be viewed as a doped substrate
with two insets of the opposite doped type material; the substrate is the
body while the insets are the source and the drain.
4.1.1 We learned that applying a voltage to the gate terminal of the same
type as the substrate (positive voltage for a p-type substrate, inverse)
induces a conducting channel between the two insets; a current will flow if
there is a voltage difference between the source and the drain.
4.2 We learned that, for a constant voltage between the gate and source
with increasing voltage between source and drain, the MOSFET will
eventually get to the saturation region, where the current no longer
increases, regardless of the increase in voltage between the source and
drain. Before reaching the saturation region, the MOSFET is in the linear
region.
Very good!
Week ending July 4, 2013
Here is what I learned from chapter 2 (Didoes):
- Diodes in order to generate function of Vo in terms of Vi using resistors, diodes and DC batteries
parallel to the output load.
which is wave shaping in a way.
- Diodes and capacitors of good quality can be used in order to generate a voltage multiplier as the
voltage across the capacitor is detecting the peak amplitude and the one across the diode is the one
clamped.
- Zener Diodes can be used to design shunt voltage regulators and they do a better job than regular
diodes in series because of it has a smaller dynamic resistance through it.
- Diodes can be used to build logic gate circuits.
- Diodes have different models to use: ideal, constant voltage drop, piece wise linear, exponential.
Good. The English phrasing need to be adjusted to improve clarity.
Week ending, July 12, 2013
3.5 We learned three different ways of biasing a BJT for use as an amplifier. The methods are: a
current source on the emitter branch, four resistors (one on the collector, one on the emitter and
two coming from the base and going to different DC sources) and a feedback resistor, where the
collector and base are connected with a resistor.
3.6 We learned about the two small signal equivalent circuits for a BJT; a small signal means
that the base-emitter voltage is less than the thermal voltage. For the hybrid-pi model, three
values are needed: the trans-conductance (the DC collector current divided by the thermal
voltage), the pi-resistance (beta divided by the trans-conductance) and the output resistance (the
Early voltage divided by the DC collector current). Using this model, a BJT can act as a
resistance or an amplifier.
3.7 We learned that a common terminal amplifier has one terminal that is not the input or the
output for the signal but is connected to the ground instead, either directly or through a resistor.
4.3 We learned about the I-V equation models for NMOS and PMOS, for both the linear region
and the saturation region. The saturation equation, called the square-law equation, can be found
directly from the linear equation and the saturation condition. We also learned about the body
effect, which occurs when there is a potential difference between the source and the body, the
temperature effect, which causes current to decrease with increasing temperature and breakdown,
which can be harmless diode breakdown or damaging breakdown at the gate.
4.4 In this topic that was not covered in class, we learned how to use the I-V equations to
evaluate biasing of a MOSFET.
4.5 We learned about the two small signal models for a MOSFET, which are similar to the BJT
models except for the fact that there is no resistance between the base and the emitter. The transconductance can be derived from the square law equation. This small signal model holds when
the voltage between the gate and the source is smaller than the overdrive voltage.
Good!
Week ending July 26, 2013
3.7 We learned about common emitter (CE), common base (CB) and common collector (CC)
BJT amplifiers; we saw CE and CB both with and without a resistance on the common terminal.
We calculated gain, input resistance and output resistance for each amplifier. We also saw that
the input resistance for the CC is high, the output resistance is low, and the gain is close to unity,
which makes a CC amplifier useful as a voltage follower.
4.6 We learned about several different applications of the ac equivalent model of a MOSFET.
These include using the MOSFET as an active load with value 1/gm or ro, and using MOSFETs
to make a voltage reference circuit.
4.7 We learned about the common source configuration of a MOSFET amplifier. Just as for the
common emitter, we saw examples with and without a resistor on the common terminal and we
calculated gain, input resistance and output resistance.
Very good!