Attenuator Bridged T Excel計算器

pprichard

可以簡單地輸入特性阻抗計算出需要的電阻值，或輸入電阻值計算出特性阻抗..

pprichard

汪洋大海 发表于 2019-9-6 09:31
https://www.eda365.com/thread-188514-1-1.html

; I. Q& _3 _+ ?! e+ m奇怪，两者对比，偏差有点大。

Bridged-T Attenuator Example
A bridged-T attenuator is required to reduce the level of an 8Ω audio signal line by
: F4 b4 \. x7 ^1 l% j4dB. Calculate the values of the resistors required.

Then resistors R1 are equal to the line impedance of 8Ω, resistor R2 is equal to 13.7Ω
9 y: q# f9 u; z& j4 o, h4 z  mand the bridging resistor R3 is equal to 4.7Ω, or the nearest preferred values.
As with the standard T-pad attenuator, as the amount of attenuation required by the
circuit increases, the series bridge impedance value of resistor R3 also increase while
8 x+ L8 |: f' Q; i( n8 hthe parallel shunt impedance value of resistor R2 decreases. This is characteristic of a
4 W7 x$ [# `0 i, {; {* d5 Ysymmetrical bridged-T attenuator circuit used between equal impedances.

pprichard

汪洋大海 发表于 2019-9-6 09:31
1 w( b" c) {2 Lhttps://www.eda365.com/thread-188514-1-1.html
; h  E4 O  \# c1 x; e
奇怪，两者对比，偏差有点大。

$ ?) D  B2 w9 O# T$ v4 b  b1 tThe Bridged-T Attenuator is another resistive attenuator design which is a variation on the standard symmetrical T-pad Attenuator.
As its name implies, the bridged-T attenuator has an additional resistive element forming a bridged network across the two series resistors of the standard T-pad.
This additional resistive element enables the circuit to reduce the level of a signal by the required attenuation without changing the characteristic impedance of the circuit
$ Z" m6 I+ ]% r/ b8 ias the signal appears to “bridge” across the T-pad network. Also the two series resistances of the original T-pad are always equal to the input source and output load
4 P6 \  E, w0 F, T4 _impedances.
' j0 c2 ]8 v& X2 w- AThe circuit for a “bridged-T attenuator”, ( T ) is given below.

' @9 A" w8 F% N+ p) d
  O; w0 E( _- d7 a! L" H& U( yResistor, R3 forms the bridge network across a standard T-pad attenuator. The two series resistors, R1 are chosen to equal the source/load line impedance. One major
1 |* l) _" b7 zadvantage of the bridged-T attenuator over its T-pad cousin, is that the bridged-T pad has a tendency to match itself to the transmissions lines characteristic impedance.
( ^/ Z( d/ x# |However, one disadvantage of the bridged-T attenuator circuit is that the attenuator requires that its input or source impedance, ( Z ) equals its output or load impedance,
4 G9 M" o5 B3 f* N0 A; L( Z ) and therefore cannot be used for impedance matching.
The design of a bridged-T attenuator is as simple as for the standard T-pad attenuator. The two series resistors are equal in value to the lines characteristic
9 Q, O; G3 k, G2 f' X$ Eimpedance and therefore require no calculation. Then the equations given to calculated the parallel shunt resistor and the additional bridging resistor of a bridged-T attenuator circuit used for impedance matching at any desired attenuation are given as:
Bridged-T Attenuator Equations:


+ r5 ]# u! z/ t* x- ewhere: K is the impedance factor, and Z is the source/load impedance.
0 ~6 w' r& F; ]) y7 z% P
6 m& F9 S+ L; o

汪洋大海

https://www.eda365.com/thread-188514-1-1.html

奇怪，两者对比，偏差有点大。

汪洋大海