Wideband attenuator circuits and methods
Embodiments of the present invention include wideband attenuator circuits and methods. In one embodiment the present invention includes a first divider circuit coupled in series with two or more second divider circuits. The divider circuits include resistance and capacitance values that may be set according to particular relationships. In one embodiment, a wideband attenuator may include capacitors that are selectively coupled to each output node.
1. An attenuator comprising:
a first divider circuit comprising a first resistance coupled between a first output node and a reference voltage, a first capacitance coupled between the first output node and the reference voltage, a second resistance coupled between a first input node and the first output node, and a second capacitance coupled between the first input node and the first output node; and
two or more second divider circuits each comprising a third resistance coupled between a second output node and the reference voltage, a third capacitance coupled between the second output node and the reference voltage, a fourth resistance coupled between a second input node and the second output node, and a fourth capacitance coupled between the second input node and the second output node,
wherein each of the two or more second divider circuits are coupled in series and the first divider circuit is coupled to a second output node of the last second divider circuit in the series, and wherein the first divider circuit further includes a fifth capacitance and a first switch for selectively coupling the fifth capacitance in parallel with the first resistance, and wherein said two or more second divider circuits further include two or more second switches for selectively coupling the third capacitance in parallel with the third resistance.
2. The attenuator of claim 1 wherein the product of the first resistance and the sum of the first capacitance and fifth capacitance, the product of the second resistance and second capacitance, and the product of the third resistance and third capacitance are equal.
3. The attenuator of claim 1 wherein a buffer is coupled between said attenuator and an amplifier.
4. The attenuator of claim 1 further comprising a plurality of output switches each having a first terminal coupled to one of said output nodes.
5. The attenuator of claim 4 wherein a first output switch in said plurality of output switches is coupled to the first output node, and when said first output switch is closed, said first switch is open and the two or more second switches are closed.
6. The attenuator of claim 4 wherein a first output switch in said plurality of output switches is coupled to a selected output node of the two or more second output nodes, and when said first output switch is closed, said first switch is closed, a first switch of the two or more second switches that is coupled to the selected output node is open, and the other two or more second switches are closed.
7. An attenuator comprising:
a first resistor having a first resistance value coupled between a first node and a reference voltage;
a first capacitor having a first capacitance value coupled between the first node and the reference voltage;
a second resistor having a second resistance value coupled between a second node and the first node;
a second capacitor having a second capacitance value coupled between the second node and the first node;
a third resistor having a third resistance value coupled between the second node and the reference voltage;
a third capacitor having a third capacitance value selectively coupled between the second node and the reference voltage;
a fourth resistor having a fourth resistance value approximately equal to the second resistance value coupled between a third node and the second node;
a fourth capacitor having a fourth capacitance value approximately equal to the second capacitance value coupled between the third node and the second node;
a fifth resistor having a fifth resistance value approximately equal to the third resistance value coupled between the third node and the reference voltage;
a fifth capacitor having a fifth capacitance value approximately equal to the third capacitance value selectively coupled between the fourth node and the reference voltage;
a sixth resistor having a sixth resistance value approximately equal to the second resistance value coupled between a fourth node and the third node;
a sixth capacitor having a sixth capacitance value approximately equal to the second capacitance value coupled between the fourth node and the third node; and
a seventh capacitor selectively coupled between the first node and the reference voltage.
8. The attenuator of claim 7 wherein the product of the first resistance value and the sum of the first and seventh capacitance values, the product of the second resistance value and second capacitance value, and the product of the third resistance value and third capacitance value are equal.
9. The attenuator of claim 7 further comprising a first switch coupled to the first node, a second switch coupled to the second node, a third switch coupled to the third node, and a fourth switch coupled to the fourth node.
10. The attenuator of claim 9 wherein when the first switch is closed, the fifth capacitor is coupled to the third node, the third capacitor is coupled to the second node, and the seventh capacitor is decoupled from the first node.