Title:
カットオフ周波数の変動が最小化されたフィルタ
Document Type and Number:
Japanese Patent JP3822105
Kind Code:
B2
Abstract:
A filter having a semiconductor chip and a low pass filter section on the chip. The low pass filter section includes a filter transconductor and a filter capacitor connected to the filter capacitor. The low pass filter section has a cut-off frequency related to the transconductance, gmF, of the filter transconductor and the capacitance of the filter capacitor. A gm control circuit having a control circuit transconductor is provided. The gm control circuit includes a first oscillator for producing a reference frequency. The first oscillator has a portion thereof on the chip and an off-chip capacitor and off-chip resistor. The reference frequency is a function of the capacitance of the off-chip capacitor and the resistance of the off-chip resistor. A second oscillator is on the chip and produces a variable frequency. The second oscillator has an on-chip capacitor. The variable frequency is a function of the capacitance of the on-chip capacitor and on-chip transconductor, gmC, such variable frequency is controlled by a control circuit transconductor control signal. A control loop is provided. The control loop is responsive to a difference between the reference frequency and the variable frequency and such loop produces the a feedback signal to drive the variable frequency towards the reference frequency.
Inventors:
Goldferb Marquee
Palmer Win Tea
Palmer Win Tea
Application Number:
JP2001527427A
Publication Date:
September 13, 2006
Filing Date:
September 28, 2000
Export Citation:
Assignee:
Analog Devices Incorporated
International Classes:
H03H11/04; H03H11/12
Domestic Patent References:
| JP10079643A | ||||
| JP7202632A | ||||
| JP7007374A | ||||
| JP7212188A | ||||
| JP11511300A |
Foreign References:
| US5570049 | ||||
| US5296822 | ||||
| WO2001024353A1 |
Attorney, Agent or Firm:
Kenji Yoshida
Jun Ishida
Jun Ishida