Useful Formulae. Electrical symbols and units

Transcription

1 Ueful Formulae Electrical ymbol and unit Quantity Symbol Unit bbreiated unit ngle radian or degree Rad or aacitance Farad F arge Q oulomb onductance G Siemen S urrent I mere Energy J Joule J Flux Weber Wb Flux denity B Tela T Frequency f Hertz Hz Imedance Z Om Ω Inductance L Henry H Power P Watt W Reactance X Om Ω Reitance R Om Ω Time t econd oltage olt arge, current and oltage Q = I t Om Law = I R and I = / R and R = / I Similarly if reitance i relaced by reactance or imedance: = I X and I = / X and X = / I = I Z and I = / Z and Z = / I Power and energy P = I and P = 2 / R and P = I 2 R J = P t and ince P = I o J = I t

2 Reitor in erie RT = R + R2 + R3 Reitor in arallel R R2 but were tere are only two reitor RT R R R R R R T aacitance were i te ermittiity of te dielectric and = 0 r d aacitance, carge and oltage Q = Inductance 2 L n were µ i te ermeability of te magnetic medium and µ = µ0 µr l Energy tored in a caacitor J = ½ 2 Energy tored in an inductor J = ½ L I 2 Inductor in erie L T = L + L 2 + L 3 Inductor in arallel L L2 but were tere are only two inductor LT L L L L L L T 2 3 aacitor in erie T but were tere are only two caacitor T aacitor in arallel T =

3 Induced e.m.f. in an inductor di e L were di dt dt i te rate of cange of current wit time urrent in a caacitor d i were d dt dt i te rate of cange of oltage wit time Sine wae oltage = max in( t) or = max in(2 f t) becaue = 2 f f = / T were T i te eriodic time For a ine wae, to conert: RMS to eak multily by.44 Peak to RMS multily by Peak to aerage multily by Peak to eak-eak multily by 2 aacitie reactance Inductie reactance X = I = 2f XL = I L L = 2fL Reitance and reactance in erie 2 2 Z = R X Reonance and = arctan X R XL = X tu L = fo = 2 L Q = R L Bandwidt = Q fo or 2 fo L = 2fo Power factor Power factor = True ower/arent ower = Watt / olt-amere = W / True ower = (I co ) = I co Power factor = co = R / Z Reactie ower = (I in ) = I in 3

4 Biolar junction tranitor (BJT) Tranitor junction current equation IE = IB + I Large ignal (or d.c.) common emitter current gain FE I I B Small ignal (or a.c.) common emitter current gain fe I I B (Δ i a mall cange) ollector ower diiation P = I E Total ower diiation PT = P + PB = (I E) + (IB BE) PT I E wen FE i large Junction gate field effect tranitor (JFET) Large ignal (or d.c.) common ource forward tranfer conductance Small ignal (or a.c.) common ource forward tranfer conductance Total ower diiation PT = ID DS g g FS f ID I GS D GS Power ulie Outut reitance R I Regulation = in 00% mlifier oltage gain urrent gain i in Iin I P Power gain P i in Gain wit negatie feedback G (wen β i large, G ) 4

5 Generalied mall ignal ybrid (-) arameter Inut reitance i in in Reere tranfer oltage ratio r Iin Forward current tranfer ratio f I I Outut conductance o Iin ommon emitter mall ignal -arameter Inut reitance ie be be Reere tranfer oltage ratio re Ib ce Forward current tranfer ratio fe I I c c Outut conductance oe Ib ce R fe L ommon emitter amlifier oltage gain Oerational amlifier ie oltage gain db or 20log0 in in Slew rate R be F Inerting amlifier oltage gain t in RI 0.59 Lower cut-off frequency of an inerting amlifier f 2 R R I I I I 0.59 Uer cut-off frequency of an inerting amlifier f 2 2 R R F F F F Bandwidt f2 f F RF 2I RI FRF IRI 5

6 Ocillator Gain wit oitie feedback G (wen β, G ) Ladder network ocillator (wit tree R ection) f 2 6R Wien bridge ocillator (wit ==2= and R=R=R2) f 2R Gain wit negatie feedback G (wen β i large, G ) table multiibrator (wit ==2= and R=R=R2) T =.4 R Timer Monotable mode T =. R table mode ton = 0.693(R+R2) toff = 0.693R2 T = ton+toff = 0.693(R+2R2) Pule reetition frequency.44. r. f. ( R 2 R ) 2 t R R Mark to ace ratio t R on 2 off 2 t R R t t R 2R on 2 Duty cycle = 00% on off 2 Tranformer Flux equation in(2 ft) max Primary oltage 4.44 fmax Secondary oltage 4.44 fmax oltage and turn ratio Turn er olt For more information and oter reource leae go to: tt:// 6