1. Elektronika SMA “MIMI” Surabaya Guru Mata Pelajaran :
Onie Meiyanto, S.Pd.
Jadual Pelajaran : Senin jam ke- 6,7
SMA “MIMI”
Surabaya

3. Basic electronics

4. Ohm’s law V1 I R V2 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 R I V2

5. Schematics Symbols represent circuit elements Lines are wires Battery+
Battery
Sample circuit V + I R
Resistor
Ground
Ground voltage
defined = 0

6. Parallel and series resistors
same current flows through all
Parallel
save voltage across all
Series circuit
V = R1 I + R2 I = Reff I
Reff = R1 + R2 +
Note: these points are
connected together I V R1 R2
Parallel circuit
I = V/R1 + V/R2 = V/Reff
1/Reff = 1/R1 + 1/R2 + V R1 R2 I1 I2 I

7. 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 << R2
Resistive divider
I = Vin/Reff = Vout/R2
Vout = Vin (R2 / (R1 + R2) ) +
Vin R1 R2 I
Vout
New schematic symbol:
external connection

8. 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

9. 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
Vout t
Vin
t = RC
Capacitor charging curve
time constant = RC
New schematic
symbol:
capacitor + V R C I
Vout Q
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))

10. AC circuits C R 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) R
I =
(V0/R) cos(2 p f t)
Resistive ac circuit
New schematic
symbol:
AC voltage source
V0 cos(2 p f t) C
I =
- 2 p f CV0 sin(2 p f t)

11. 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

12. Explore capacitor circuits
Impedance ZC = 1/ (2 p j f C)
Limit of low frequency f ~ 0
ZC --> infinity
Capacitor is open circuit at low frequency
Limit of low frequency f ~ infinity
ZC --> 0
Capacitor is short circuit at low frequency
Capacitive ac circuit
V0 cos(2 p f t) C
I = V/ZC

13. 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
Capacitor charging circuit
= Low-pass filter
Vin = V0 cos(2 p f t) R C I
Vout
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 )

14. Capacitor charging circuit
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
Vin = V0 cos(2 p f t) R L I
New schematic
symbol:
Inductor
Vout
logVin
log(Vout)
f = R / 2 p j L
log( f )

15. Capacitor filters circuits
Can make both low and high pass filters
Low-pass filter
Vin = V0 cos(2 p f t) R C I
Vout
High-pass filter
Vin = V0 cos(2 p f t) C R I
Vout
log(Vout)
log( f )
logVin
f = 1 / 2 p t
Gain response
knee
log(Vout)
log( f )
logVin
f = 1 / 2 p t
Gain response
phase
log( f )
f = 1 / 2 p t
Phase response
-90 degrees
phase
log( f )
f = 1 / 2 p t
Phase response
-90 degrees
0 degrees
0 degrees

16. Summary of schematic symbols
Potentiometer
Resistor +
Battery
Potentiometer
2-inputs plus
center tap
Capacitor
AC voltage
source
Inductor
Diode
Ground
Non-connecting
wires
External
connection - +
Op amp

17. Color code Color black brown red orange yellow green blue violet gray
Resistor values determined by color
Three main bands
1st = 1st digit
2nd = 2nd digit
3rd = # of trailing zeros
Examples
red, brown, black
no zeros = 21 Ohms
yellow, brown, green
= 4.1 Mohm
purple, gray, orange
= 78 kOhms
Capacitors can have 3 numbers
use like three colors
Color
black
brown
red
orange
yellow
green
blue
violet
gray
white
Number 1 2 3 4 5 6 7 8 9