Electronics Formulas
Essential formulas every electronics engineer needs. Quick reference for design and analysis.
Ohm's Law & Power
V = I × R
P = V × I = I² × R = V² / R
P = V × I = I² × R = V² / R
Fundamental relationship between voltage, current, resistance, and power.
RC Time Constant
τ = R × C
V(t) = V0 × (1 - e-t/τ)
V(t) = V0 × (1 - e-t/τ)
Charging and discharging behavior of RC circuits.
Reactance & Impedance
XL = 2πfL
XC = 1 / (2πfC)
Z = √(R² + (XL - XC)²)
XC = 1 / (2πfC)
Z = √(R² + (XL - XC)²)
Inductive and capacitive reactance, total impedance in AC circuits.
Voltage Divider
Vout = Vin × R2 / (R1 + R2)
Simple resistive divider — most used formula in analog design.
Op-Amp Gain
Av = -(Rf / Rin) [Inverting]
Av = 1 + (Rf / Rg) [Non-Inverting]
Av = 1 + (Rf / Rg) [Non-Inverting]
Closed-loop gain for inverting and non-inverting operational amplifier configurations.
dB Conversion
dB = 20 × log10(Vout / Vin)
dB = 10 × log10(Pout / Pin)
dB = 10 × log10(Pout / Pin)
Decibel conversion for voltage and power ratios.