Transcript Capacitors and Inductors

SMV ELECTRIC
TUTORIALS
Nicolo Maganzini, Geronimo Fiilippini, Aditya Kuroodi
2015
OPERATIONAL
AMPLIFIERS
What are we learning?

Learning about operational amplifiers

What they do and how they are used.

Increasing signal strength and filtering. Medical station
pulse sensor.

Learn about how they are nearly ideal for DC
amplification.

Learn about different Op-Amp circuits:

Inverting

Noninverting

Voltage Follower (Buffer)
Op-Amp connections

Three-terminal device:

Inverting input (-)

Noninverting input (+)

Output

Power supply + lead (+ Vss)

Power supply – lead (- Vss)
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Real device
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What does it do?

Amplifies the signal:

Two inputs and one output:


𝑉𝑜𝑢𝑡 = 𝐺0 𝑉+ − 𝑉−

Takes difference of two input
signals, multiplies by 𝐺0 and outputs
the new voltage.
BUT: This works only if 𝑉𝑜𝑢𝑡 < +𝑉𝑠𝑠 ; 𝑉𝑜𝑢𝑡 > −𝑉𝑠𝑠

I.e. If op-amp powered at 9V, it can get small
signals and make them as big as 9V.
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+𝑉𝑠𝑠
−𝑉𝑠𝑠
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Biasing circuits

PROBLEM:


𝐺0 =
1 Million.

Say you have 𝑉+ = 0.5 𝑉 and 𝑉− = 0𝑉, output would be
500,000 V.

BUT WE DON’T NEED THAT MUCH!! What do we do?
Create stabilizing circuits around the op-amp that make
it useful.
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But first, some properties

High input impedance:


At 𝑉+ and 𝑉− , voltage is ‘read’ like a sensor, but no current
is drawn inside the op amp.
Low output impedance:

At 𝑉𝑜𝑢𝑡 , the current that can be produced is limited only
by the power supply
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Inverting amplifier
 𝑉𝑜𝑢𝑡
= −𝑉𝑖𝑛
𝑅𝑓
𝑅𝑖𝑛

With this circuit, signal is amplified and flipped
upside down.

𝑉+ is connected to ground, so 0 − 𝑉− = −𝑉−

i.e. Signal is inverted.

Larger 𝑅𝑓 means more amplification,

Larger 𝑅𝑖𝑛 means less amplification.

Important feature: Can be used to
de-amplify signal.

Used in medical station
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Non-inverting amplifier
𝑅2
+
𝑅1

𝑉𝑜𝑢𝑡 = 𝑉𝑖𝑛 1

With this circuit, signal is amp.

The two resistors form a
potential divider.

Large 𝑅2 means more amp,

Large 𝑅1 means less amp.

Signal is not inverted.
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Buffer amplifier

𝑉𝑖𝑛 = 𝑉𝑜𝑢𝑡

Why would we ever need this????

Separates parts of the circuits and makes them
independent.

If one part of the circuit cannot supply a lot of current,
but has a voltage signal, add a buffer.


Now you have the same voltage signal but with as much
current as you want.
Also used in the medical station.
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Buffer Circuit Project

Use a 9V battery to make a potential divider that makes
a 4.5V signal. Use 1KOhm resistors.

Now use that signal to drive a fan.

While the fan is connected, measure the voltage of the
signal. Has it changed? Is it still constant? Why?

Take notes on what you do and what the answer is on
a piece of paper.
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Continued

Now using the same potential divider, add a buffer to the
signal and then drive the fan with the buffer. Power it
with another battery.
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How about using our photosensor?

Replace resistor with photocell.


Will the motor turn on when photocell is covered or
uncovered?
Can you change that behavior?
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DIGITAL AND
ANALOG SIGNALS
BREADBOARDING
Breadboard is a way of constructing electronics without
having to use a soldering iron.
SOLDERLESS
BREADBOARD
What a solderless breadboard looks from the inside.
SIGNALS
A signal is any kind of physical quantity that conveys information.
Audible speech, hand gestures, sound, light, pressure, electrical signals
In circuits, the word signal will be used in reference to an electrical quantity of voltage or current that is used to represent or signify some other physical quantity.
Signal from a thermometer, sound sensor, GPS, light sensor
Two main types of signals
Analog signals
Digital signals
ANALOG AND
DIGITAL SIGNALS
Analog
Continuous (no breaks or
interruptions)
Examples:
• music from speakers
Digital
Not continuous. Use
specific values to
represent information.
Examples:
• Light turning on and off
• Computer signals
ANALOG AND
DIGITAL SIGNALS
Is this a digital signal??
Even though this signal has more than two possible values (unlike the one on the previous slide), it is still considered a digital signal because only a finite amount of values are allowed.
ANALOG AND
DIGITAL SIGNALS
Converting from analog to digital (ADC)
Trying to represent analog signal as best as we can using
“discrete” values.
SIGNAL
FREQUENCIES AND
PERIODS
Frequency is the number of occurrences of a repeating
event per unit time.
# 𝑜𝑓 𝑜𝑐𝑐𝑢𝑟𝑟𝑒𝑛𝑐𝑒𝑠
𝑓=
𝑒𝑙𝑎𝑝𝑠𝑒𝑑 𝑡𝑖𝑚𝑒
Period is the duration of one cycle in a repeating event.
Period (𝑇) is the reciprocal of the frequency.
1
𝑓=
𝑇
Frequency measured in hertz (Hz).
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SIGNAL
FREQUENCIES AND
PERIODS
We can also get the period from the plots, by measuring how
long it takes for the signal to complete one cycle.
EXCERCISE:
Calculate period and the fundamental frequency of
the following signal: