Elektronika

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Elektronika

• Guru Mata Pelajaran
• Onie Meiyanto, S.Pd.
• Jadual Pelajaran Senin jam ke- 6,7
• E-mail onie_204_at_yahoo.com

SMA MIMI Surabaya
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Basic electronics
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Ohms law

• Current voltage / resistance
• I V / R
• V I x R
• Definitions
• Voltage potential energy / unit charge, units
  Volts
• Current charge flow rate, units Amps
• Resistance friction, units Ohms
• Example
• Voltage drop when current flows through resistor
• V1 - V2 I R

V1
I
R
V2
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Schematics

• Symbols represent circuit elements
• Lines are wires

Battery
Sample circuit
V
I
R
Resistor
Ground
Ground voltage defined 0
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Parallel and series resistors

• Series
• same current flows through all
• Parallel
• save voltage across all

Series circuit V R1 I R2 I Reff I Reff R1
R2
Parallel circuit I V/R1 V/R2 V/Reff 1/Reff
1/R1 1/R2
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Resistive voltage divider

• Series resistor circuit
• Reduce input voltage to desired level
• Advantages
• simple and accurate
• complex circuit can use single voltage source
• Disadvantage
• dissipates power
• easy to overload
• need Rload ltlt R2

Resistive divider I Vin/Reff Vout/R2 Vout
Vin (R2 / (R1 R2) )
New schematic symbol external connection
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Variable voltage divider

• Use potentiometer ( variable resistor)
• Most common constant output resistance

Variable voltage divider Vout Vin (Rout / (Rvar
Rout) )
New schematic symbol potentiometer
I
Vout
Vin
Rvar
Rout
I
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Capacitors

• Charge voltage x capacitance
• Q C V
• Definitions
• Charge integrated current flow , units
  Coloumbs Amp - seconds
• I dQ/dt
• Capacitance storage capacity, units Farads
• Example
• Capacitor charging circuit
• Time constant RC t

Capacitor charging circuit V VR VC R dQ/dt
Q/C dQ/dt Q/RC V/R Q C V (1 -
exp(-t/RC)) Vout Vin (1 - exp(-t/RC))
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AC circuits

• Replace battery with sine (cosine) wave source
• V V0 cos(2 p f t)
• Definitions
• Frequency f cosine wave frequency, units
  Hertz
• Examples
• Resistor response I (V0/R) cos(2 p f t)
• Capacitor response Q CV0 cos(2 p f t)
• I - 2 p f CV0 sin(2 p f t)
• Current depends on frequency
• negative sine wave replaces cosine wave
• - 90 degree phase shift lag

• Capacitive ac circuit
• 90 degree phase lag

V0 cos(2 p f t)
C
I - 2 p f CV0 sin(2 p f t)
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Simplified notation ac-circuits

• V V0 cos(2 p f t) V0 exp(2 p j f t)
  c.c./2
• Drop c.c. part and factor of 1/2
• V V0 exp(2 p j f t)
• Revisit resistive and capacitive circuits
• Resistor response I (V0/R) exp(2 p j f t) V
  / R V/ ZR
• Capacitor response I 2 p j f CV0 exp(2 p j f
  t) (2 p j f C) V V/ ZC
• Definition Impedance, Z effective resistance,
  units Ohms
• Capacitor impedance ZC 1 / (2 p j f C)
• Resistor impedance ZR R
• Impedance makes it look like Ohms law applies to
  capacitive circuits also
• Capacitor response I V / ZC

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Explore capacitor circuits

• Impedance ZC 1/ (2 p j f C)
• Limit of low frequency f 0
• ZC --gt infinity
• Capacitor is open circuit at low frequency
• Limit of low frequency f infinity
• ZC --gt 0
• Capacitor is short circuit at low frequency

Capacitive ac circuit
V0 cos(2 p f t)
C
I V/ZC
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Revisit capacitor charging circuit

• Replace C with impedance ZC
• Charging circuit looks like voltage divider
• Vout Vin (ZC / (ZR ZC) ) Vin / (1 2 p j f
  R C )
• Low-pass filter
• Crossover when f 1 / 2 p R C 1 / 2 p t , t
  is time constant
• lower frequencies Vout Vin pass band
• higher frequencies Vout Vin / (2 p j f R C )
  attenuated

• Low-pass filter response
• time constant RC t

logVin
Single-pole rolloff 6 dB/octave 10 dB/decade
knee
log(Vout)
f 1 / 2 p t
log( f )
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Inductors

• Voltage rate of voltage change x inductance
• V L dI/dt
• Definitions
• Inductance L resistance to current change,
  units Henrys
• Impedance of inductor ZL (2 p j f L)
• Low frequency short circuit
• High frequency open circuit
• Inductors rarely used

Capacitor charging circuit Low-pass filter
High-pass filter response
logVin
Vout
log(Vout)
f R / 2 p j L
log( f )
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Capacitor filters circuits

• Can make both low and high pass filters

0 degrees
0 degrees
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Summary of schematic symbols
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Color code

• Resistor values determined by color
• Three main bands
• 1st 1st digit
• 2nd 2nd digit
• 3rd of trailing zeros
• Examples
• red, brown, black
• 2 1 no zeros 21 Ohms
• yellow, brown, green
• 4 1 5 4.1 Mohm
• purple, gray, orange
• 7 8 3 78 kOhms
• Capacitors can have 3 numbers
• use like three colors

Color black brown red orange yellow green blue vi
olet gray white
Number 0 1 2 3 4 5 6 7 8 9