Claims
- 1. An apparatus for providing an adjustable bandwidth high pass filter, the apparatus comprising:
a highpass filter having an input capacity in series with a resistive ladder having a plurality of resistances coupled in series, said coupling between the capacity and the first resistor of the resistive ladder defining a first tap and successive couplings between resistances forming successive taps, the last resistance of said resistive ladder being coupled to a ground; a plurality of bandwidth adjusting resistances, each first side of the bandwidth adjusting resistance coupled to the first tap; and a plurality of switches that provide the coupling of the second side of each of the bandwidth adjusting resistances to said ground.
- 2. An apparatus as in claim 1, wherein said ground comprises an AC ground, said AC ground providing a DC bias.
- 3. An apparatus as in claim 1 wherein the switches further comprise semiconductor switches.
- 4. An apparatus as in claim 3 wherein the semiconductor devices further comprise MOSFETS (Metal Oxide Semiconductor Field Effect Transistors).
- 5. An apparatus as in claim 4 wherein the MOSFET is a N-type MOSFET.
- 6. An apparatus as in claim 4 wherein the MOSFET is a P type MOSFET.
- 7. An apparatus as in claim 1 wherein the apparatus further comprises:
a MOSFET device having a source, a gate and a drain the source coupled to the second side of one of said bandwidth adjusting resistors; the drain of the MOSFET device coupled to said ground and said gate being coupled to a control circuit.
- 8. An apparatus as in claim 7 wherein the control circuit comprises:
an amplifier output coupled to the gate of the switching device.
- 9. An apparatus as in claim 8 wherein the amplifier further comprises:
a tristate buffer amplifier; and a pull up resistance coupled between the output of the tristate and a power supply.
- 10. An apparatus as in claim 9 wherein the power supply is the power supply for an integrated circuit containing the apparatus.
- 11. An apparatus as in claim 9 wherein the pull up resistance comprises a long channel triode device.
- 12. An apparatus in claim 7 further comprising a capacity disposed between the gate and source of the MOSFET switch.
- 13. An apparatus as in claim 11 wherein the drain of the long channel triode device is coupled to a power supply voltage, the gate is coupled to the ground of the power supply voltage and the source is coupled to the gate of the MOSFET switch.
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This Application claims Priority From Provisional Application No. 60/164,970 filed Nov. 11, 1999.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60164970 |
Nov 1999 |
US |
Continuations (1)
|
Number |
Date |
Country |
Parent |
09712414 |
Nov 2000 |
US |
Child |
10760492 |
Jan 2004 |
US |