3 Basic Electronics 3

Basic electronics Optical interfaces: Detect and control

Ohm’s law ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],I R V 1 V 2

Schematics ,[object Object],[object Object],Battery Resistor Ground V R I Sample circuit Ground voltage defined = 0 + +

Parallel and series resistors ,[object Object],[object Object],[object Object],[object Object],Series circuit V = R 1 I + R 2 I = R eff I R eff = R 1 + R 2 Parallel circuit I = V/R 1 + V/R 2 = V/R eff 1/R eff = 1/R 1 + 1/R 2 + Note: these points are connected together I V R 1 R 2 + V R 1 R 2 I 1 I 2 I

Resistive voltage divider ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],New schematic symbol: external connection Resistive divider I = V in /R eff = V out /R 2 V out = V in (R 2 / (R 1 + R 2 ) ) + V in R 1 R 2 I I V out

Variable voltage divider ,[object Object],[object Object],V in R var R out I I V out Variable voltage divider V out = V in (R out / (R var + R out ) ) New schematic symbol: potentiometer +

Capacitors ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Capacitor charging circuit V = V R + V C = R dQ/dt + Q/C dQ/dt + Q/RC = V/R Q = C V (1 - exp(-t/RC)) V out = V in (1 - exp(-t/RC)) New schematic symbol: capacitor + V R C I V out Q V out t V in  = RC Capacitor charging curve time constant = RC

AC circuits ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],V 0 cos(2  f t) C I = - 2  f CV 0 sin(2  f t) ,[object Object],[object Object],V 0 cos(2  f t) R I = (V 0 /R) cos(2  f t) Resistive ac circuit New schematic symbol: AC voltage source

Simplified notation: ac-circuits ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Explore capacitor circuits ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],V 0 cos(2  f t) C I = V/Z C Capacitive ac circuit

Revisit capacitor charging circuit ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],log(V out ) log(  f ) logV in f = 1 / 2  ,[object Object],[object Object],Single-pole rolloff 6 dB/octave = 10 dB/decade knee Capacitor charging circuit = Low-pass filter V in = V 0 cos(2  f t) R C I V out I

Inductors ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Capacitor charging circuit = Low-pass filter V out log(V out ) log(  f ) logV in f = R / 2  j  L High-pass filter response V in = V 0 cos(2  f t) R L I I New schematic symbol: Inductor

Capacitor filters circuits ,[object Object],0 degrees 0 degrees Low-pass filter V in = V 0 cos(2  f t) R C I V out I High-pass filter V in = V 0 cos(2  f t) C R I V out I log(V out ) log(  f ) logV in f = 1 / 2  Gain response log(V out ) log(  f ) logV in f = 1 / 2  Gain response knee phase log(  f ) f = 1 / 2  Phase response -90 degrees phase log(  f ) f = 1 / 2  Phase response -90 degrees

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

Color code ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Color black brown red orange yellow green blue violet gray white Number 0 1 2 3 4 5 6 7 8 9

3 Basic Electronics 3

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3 Basic Electronics 3