Voltage divider - loaded and open-circuit dB calculator damping volts potentiometer circuit impedance damping pad decibel dB voltage attenuator impedance bridging matching - sengpielaudio Sengpiel Berlin

Using impedance matching or power matching you make the output impedance of a source equal
to the input impedance of the load to which it is ultimately connected. T- and H-pads are used in radio
frequency (RF) circuits to attenuate a signal (damping). It is applied where maximum energy (power) is
transferred between a source and a load. Then Z_source = Z_load.
 
But in sound recording (audio), public address, and HiFi only impedance bridging is used with:  
Z_source << Z_load or Z_S << Z_L or Z_out << Z_in  
The output impedance of the source is always much smaller than the input impedance of the load.
In this case never try to calculate and use T- and H-pads circuits - better use voltage dividers instead.
asymmetric                   symmetric
 
Historical reasons show impedance values especially of 50 ohms, 200 ohms, or 600 ohms.
Voltage Divider Calculator No. 1  
Entering three or four values calculate the others. The value of Z_load can be entered additionally,
otherwise it uses automatically a 1 megohm load - unloaded open circuit.
Use the left mouse button - click at a free space.

V_unloaded means V_out without Z_L. If wanted, Z_source of the generator can be added to Z₁.

A negative solution means damping (loss) - positive solution means amplification (gain).

Voltage damping:  

Output voltage:  

Parallel resistance:  

See also: Calculation of damping
Impedance bridging or Voltage bridging Zout < Zin

Voltage Divider Calculator No. 2

This calculator, given any three or four of the five possible values, will give the
results for the remaining one. The Z_L value is optional, if not supplied, the
calculator uses 1 Megohm. Usefull if you need to enter V_out.
Fill in any three or four fields in the form below, then click the "calculate" button.
The remaining field will be calculated, and the results displayed. If you make a
new calculation, use always the "reset" button to clear all the boxes. Z = R.

To compute Input Voltage enter Z₁, Output Voltage, and Z₂ and then click the calculate button.
To compute Z₁ enter Input Voltage, Output Voltage, and Z₂ and then click the calculate button.
To compute Z₂ enter Input Voltage, Output Voltage, and Z₁ and then click the calculate button.
To compute Output Voltage enter Input Voltage, Z₁ and Z₂ and then click the calculate button.
If wanted, Z_source of the generator can be added to Z₁.

Voltage division ratioα = Ratio (Output Voltage to Input Voltage) = V_out / V_in
Z₂ = (α × Z₁) / ( 1 − α)
dB (level) = 20 × log α
V_out = V_in × [Z₂ / (Z₁ + Z₂)]

Voltage divider (potentiometer) with different control characteristics
Figure: © Detlef Mietke − http://www.elektroniktutor.de/analog/u_teiler.html

Interconnection of two audio units equals a circuit of a voltage divider − Z2 << Z1.

Attention: The numbering of the impedances is inversely to a voltage divider.

A panpot is made of two voltage dividers: