T Attenuator
Calculator and formulas for calculating the resistances of a T attenuator
On this page, a T-pad attenuator is calculated whose resistances, i.e. the impedance, are the same on the input and output sides.
The attenuation or the voltage ratio can be entered as an argument for the calculation
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Description of the T-attenuator
A T-attenuator is a passive network that is typically used to attenuate signal strength without causing significant distortion. It consists of three resistors, with the resistors arranged in the shape of a "T".
With attenuators for high frequencies, attention must be paid to impedance matching. The input impedance and the output impedance must be equal to the wave impedance of the lines.
If the resistances on the input and output sides are not equal, impedance matching takes place at the same time as the attenuation.
Formulas for the T-attenuator
The resistances of a T-attenuator can be calculated using the following steps,
depending on the desired attenuation and the input resistance
The attenuation factor \(α\) indicates how much the signal is reduced. The following applies:
\[\displaystyle a=\frac{U_1}{U_2}= 10^{\frac{ΔL}{20 db}}\]
The resistances R1 and R2 of the T-attenuator are calculated from the impedance Z and the attenuation factor a. The damping factor a is calculated from the ratio of the output voltage to the input voltage (U1 / U2), or the damping factor ΔL in dB
\[ R_1= Z\frac{a-1}{a+1}\]
\[ R_2= Z\frac{2a}{a^2-1}\]
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