Resistor Attenuator: A resistive network that produces a reduction in amplitude. Common resistor terminators include; 'Pi' Attenuator Pads, 'L' Attenuator Pads, and 'T' Attenuator Pads. Refer below for a schematic for each of the different types of Resistor Attenuators.
Also refer to Companies that manufacture Chip Attenuators.
Note the schematics below represent attenuator pads that might be found in a chip attenuator or some other attenuator component. While the network attenuators shown in the right side-bar represent attenuators that would be used in an actual circuit design.
The physical configuration of the resistors normally sets the name of the attenuator, as found in the common designations below. However there are two sub-classes for each type, or most types. A resistor could be a balanced or unbalanced network. An unbalanced resistor network uses a common ground connection, while a balanced resistor network doesn't.
'Pi' Attenuator Pad, Balanced.
The Pi attenuator is more easily recognized in the unbalanced form. Note that the diagram in the right side-bar refers to this style as a balanced O circuit.
Balanced Resistor PI Schematic
'Pi' Attenuator Pad, Un-Balanced.
Un-Balanced Resistor PI Schematic
Some schematics may show the two grounds points connected together, or they may be shown as separate points. In either case the Surface Mount Device [SMD] may use one lead or may have two separate leads.
'T' Attenuator Pad, Balanced.
Balanced Resistor T Schematic
'T' Attenuator Pad, Un-Balanced.
The classic unbalanced T network is shown below, and two additional versions called bridged T networks are shown to the right. One version uses a tapped resistor, or what would be a 3-terminal resistor. The second version simply uses two additional resistors in parallel with the Tee portion of the network. Normally there are only a few reasons to parallel resistors, to compensate for temperature drift, to increase the power dissipation to handle the current through the node, or to obtain the correct value of resistance needed. In any case a bridged T network is identical to a T network.
Un-Balanced Resistor T Schematic
'L' Attenuator Pad, Balanced.
Note that the 'L' Pad Attenuator only requires two resistors. The 'L' Pad Attenuator is a balanced circuit, there is no un-balanced configuration. Very similar to the balanced C network shown to the right.
L Pad Attenuator
'H' Attenuator Pad, Balanced.
Two versions of the balanced H attenuator are shown to the right, which includes the bridged H attenuator.
Note that in many cases the style of attenuator may not be provided by the manufacture, just the amount of attenuation [in dB], the impedance value [50 ohms is common], and the configuration [Unbalanced is common].
Select impedance, attenuation, power rating, and frequency range if required.
The package style will normally be Surface Mount Device [SMD], but their dimensions may not be those of standard surface mount resistors. Some higher power attenuators may have a flange to dissipate more heat.