Various attenuators
・There are many kinds of attenuators
・Chip attenuators are integrated into coaxial or module type attenuators.
The function of an attenuator
Attenuators weaken (attenuate) the electrical signals to the desired level. The amount of attenuation is expressed in decibel (dB). Attenuation is typically negative value but usually omit minus ”-” when it is expressed.
Example of attenuation
How attenuators are used
Attenuators can weaken (attenuate) the electrical signals to desired level. Here are some examples:
１）Level adjusting attenuator
２）Impedance matching (as a safety device)
３）Other
Used in measurement taking advantage of wide band and linearity.
Attenuator circuit
Attenuators can be constructed using discrete resistors forming T, π, or double π shapes. In communication, the impedance must match 50Ω.
Examples of resistance combination for specific attenuation values
According to the attenuation value and the type of the circuit, the combination of resistance varies significantly. The table right shows the examples of π circuit resistance combination. These combinations also give 50Ω impedance matching.
| ATT(dB） | R1,R3(Ω） | R2(Ω） |
|---|---|---|
| 1 | 869.5 | 5.8 |
| 2 | 436.2 | 11.6 |
| 3 | 292.4 | 17.6 |
| 4 | 221 | 23.8 |
| 5 | 178.5 | 30.4 |
| 6 | 150.5 | 37.4 |
| 7 | 130.7 | 44.8 |
| 8 | 116.1 | 52.8 |
| 9 | 105 | 61.6 |
| 10 | 96.2 | 71.2 |
Chip attenuator is an integration of 3 resistors
If you use discrete resistors to form an attenuator, you need 3 resistors.
One chip attenuatorcan function as 3 discrete resistors and has the following advantages
・Guaranteed performance with one component
・Signal and ground terminals in one component simplify the PC board layout.
・Minimize parasitic capacitance and inductance
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