## Resistive ladder divider. | |

Resistive ladder dividers are built from ( mostly ) same value resistors and have same output impedance from all taps if they are driven from a low impedance.

You can find a spread-sheet with the calculations here.

Fig.1: Ladder divider.

(a): Basic circuit. If the output resistance is irrelevant, leave Rd out.

(b): Adding an "extra" Rb can in some cases reduce the tolerance requirement of Rc.

(c): If you are using arrays and have some resistors left over, adding them in the bottom of the ladder will further reduce the tolerance requirement of Rc.

This calculation assumes that Ra and k ( the gain factor ) are given:

Rout and k given:

Rin and k given:

Assuming Rc has the correct value::

To find standard values for Ra and Rb, use a voltage divider calculator like this one [1] and set:

k | Ra | Rb | Rc | Rd | Re | Rin |

-0.5 dB | 160 Ω | 2.7 kΩ | 2.700 kΩ | 151.1 Ω | N/A | 2.9 kΩ |

-1 dB | 820 Ω | 62 kΩ | 6.720 kΩ | 730.8 Ω | 7.537 kΩ | 7.5 kΩ |

-2 dB | 620 Ω | 2.4 kΩ | 2.395 kΩ | 492.5 Ω | 1 MΩ | 3.0 kΩ |

-3 dB | 470 Ω | 3.9 kΩ | 1.139 kΩ | 332.7 Ω | 1.610 Ω | 1.6 kΩ |

-4 dB | 1.1 kΩ | 5.1 kΩ | 1.881 kΩ | 694.1 Ω | 2.979 kΩ | 3.0 kΩ |

-6 dB | 750 Ω | 1.5 kΩ | 753.6 Ω | 375.9 Ω | 1.514 kΩ | 1.5 kΩ |

-8 dB | 910 Ω | 1.0 kΩ | 601.9 Ω | 362.3 Ω | 1.512 kΩ | 1.5 kΩ |

-12 dB | 3.6 kΩ | 1.6 kΩ | 1.208 kΩ | 904.3 Ω | 4.924 kΩ | 4.8 kΩ |

-16 dB | 1.2 kΩ | 270 Ω | 226.0 Ω | 190.2 Ω | 1.387 kΩ | 1.4 kΩ |

-20 dB | 1.3 kΩ | 160 Ω | 144.4 Ω | 130.0 Ω | 1.486 kΩ | 1.4 kΩ |

-32 dB | 6.8 kΩ | 180 Ω | 175.2 Ω | 170.8 Ω | 6.583 kΩ | 7.0 kΩ |

[1] | Resistive voltage divider on mustcalculate.com. |

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