Tuneable filters using operational amplifiers
AssigneeBroadcom Corporation
InventorsFrancesco Gatta, Rajeshmohan Radhamohan
Life of this patent
Estimating the term…
Abstract
A low pass filter includes a switchable resistor bank, a gain stage, and a capacitor bank. The resistors and capacitors switched into the circuit determine the cutoff frequency of the low pass filter. The frequency programmability may be obtained using the switchable resistor bank and may be implemented as a parallel bank of binary weighted resistors. Further programmability may be obtained using the switchable capacitor bank in conjunction with the switchable resistor bank. The resistor and capacitor processes in a semiconductor wafer are sufficiently accurate and repeatable so as to minimize any necessary calibration.
Claims17
A low pass filter comprising:
- a first stage including a first switchable resistor bank, a first gain stage having an input coupled to the first switchable resistor bank and an output, a first feedback capacitor coupled between the input of the first gain stage and the output of the first gain stage;
- a boost stage including a second switchable resistor bank coupled to the output of the first gain stage;
- and
- a second stage having an input coupled to an output of the boost stage including a third switchable resistor bank, a second gain stage having an input coupled to the third switchable resistor bank and an output, a second feedback capacitor coupled between the input of the second gain stage and the output of the second gain stage.
A low pass filter comprising:
- a first stage including a first switchable resistor bank, a first gain stage having an input coupled to the first switchable resistor bank and an output coupled to a second switchable resistor bank, a first feedback capacitor coupled between the input of the first gain stage and the output of the first gain stage;
- a second stage including the second switchable resistor bank, a second gain stage having an input coupled to the second switchable resistor bank and an output coupled to the fourth switchable resistor bank, a second feedback capacitor coupled between the input of the second gain stage and the output of the second gain stage;
- a boost stage including a third switchable resistor bank coupled to the output of the second gain stage;
- a third stage including the fourth switchable resistor bank, a third gain stage having an input coupled to the fourth switchable resistor bank and an output coupled to a fifth switchable resistor bank, a third feedback capacitor coupled between the input of the third gain stage and the output of the third gain stage;
- and
- a fourth stage, having an input coupled to an output of the boost stage, including the fifth switchable resistor bank coupled to the output of the third gain stage, a fourth gain stage having an input coupled to the fifth switchable resistor bank and an output, a fourth feedback capacitor coupled between the input of the fourth gain stage and the output of the fourth gain stage.
Dependencies are inferred from the claim text.