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Saturday, 22 July 2017
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  Calculate Stepped Attenuator (24 steps)


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Formulas:

Vout = Vin * R1 /(R1+R2)

Vin = Voltage input
Vout = Voltageoutput
R1 = series resistor
R2 = shunt resistor

The total resistance of the attenuator is: R1 + R2
Thate does not include any impedance after the attenuator.

To calculate the total impedance including the load on the output, calculate the parallel resistance of the load and R2, add this to the value of R1.

Example:
R1 = 50.000 ohms
R2 = 100 ohms
Rload = 50000 ohms

Rparallel = (R2 * Rload) / (R2 + Rload)
Rparallel = (100 * 50000 ) / (100 + 50000) = 99.8 ohms
Rtotal = R1 + Rparallel = 49900,2 ohms


Converting a voltage to decibels: 20 * log(n)

where n = the voltage or resistance ratio.

Example:
R1 = 50000 ohms
R2 = 100 ohms

Rtotal ( R1 + R2 ) = 50100 ohms

dB = 20 * log(R2/Rtotal)

dB = 20 * log(100/50100) = -53.99dB



Total Resistance (Rt): Ohms
  




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Search closest standard resistor value

  • E6: 20% resistors
  • E12: 10% resistors
  • E24: 5% resistors
  • E48: 2% resistors
  • E96: 1% resistors
  • E192: 0.5%, 0.25%, 0.1% resistors


  • Fill the desired value in, the closest standard value are shown in the different E serials: ohms 

    EIA Serie closest value deviation, compared
    with theoretical value
    min/max value
    E6
    E12
    E24
    E48
    E96 (recommended)
    E192