US3792367A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Active controllable filter circuit using variable transconductance amplifier
Assignee: AT&T Inc
•
Filing: 1972-05-01
•
Granted: 1974-02-12
•
Expires: 1992-05-01
Abstract
Abstract An RC active filter circuit wherein the active elements of the circuit are realized by controllable transconductance amplifiers. The transfer response of the filter circuit is readily variable by altering signals applied to the control terminals of the transconductance amplifiers.
Inventors
- 👤 P Fleischer
- 👤 D Hilberman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:26
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/0422; H03H11/0433
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
265 words
An active filter circuit comprising: first and second variable transconductance amplifiers having transconductance values g1 and g2, gain control terminals, and a first and second input terminal, respectively; a first resistor having a resistive value R1 jointly connected to an output terminal of said first amplifier and said first input terminal of said second amplifier, and to a terminal of fixed potential; a first capacitor having a capacitive value C1 connected to said first input terminal of said second amplifier and to said terminal of fixed potential and to said second input terminal of said second amplifier; a second capacitor having a capacitive value C2 jointly connected to said second input terminal of said first amplifier and an output terminal of said second amplifier, and to said terminal of fixed potential; a signal source connected to said first input terminal of said first amplifier; said output terminal of said first variable transconductance amplifier providing a filter transfer response of (g1s/C1/s2 + s/R1C1 + g1g2/C1C2) where s is the complex frequency variable; said output of said second variable transconductance amplifier providing a filter transfer response of (g1g2/C1C2/s2 + s/R1C1 + g1g2/C1C2) where s is the complex frequency variable; and means connected to said gain control terminals responsive to applied control signals for controlling and maintaining the transconductance of said amplifiers, g1 and g2, at a level such that the magnitude of the term g1g2/C1C2 is commensurate with the magnitude of the other terms in the denominators of said transfer responses, thereby insuring that said transfer responses are directly controlled by the values of g1 and g2.
Claim 2
Dependent Claim
265 words
An active filter circuit comprising: first and second variable transconductance amplifiers having transconductance values g1 and g2, gain control terminals, and a first and second input terminal, respectively; a first resistor having a resistive value R1 jointly connected to an output terminal of said first amplifier and said first input terminal of said second amplifier, and to a terminal of fixed potential; a first capacitor having a capacitive value C1 connected to said first input terminal of said second amplifier and to said terminal of fixed potential and to said second input terminal of said second amplifier; a second capacitor having a capacitive value C2 jointly connected to said second input terminal of said first amplifier and an output terminal of said second amplifier, and to said terminal of fixed potential; a signal source connected to said first input terminal of said first amplifier; said output terminal of said first variable transconductance amplifier providing a filter transfer response of (g1s/C1/s2 + s/R1C1 + g1g2/C1C2) where s is the complex frequency variable; said output of said second variable transconductance amplifier providing a filter transfer response of (g1g2/C1C2/s2 + s/R1C1 + g1g2/C1C2) where s is the complex frequency variable; and means connected to said gain control terminals responsive to applied control signals for controlling and maintaining the transconductance of said amplifiers, g1 and g2, at a level such that the magnitude of the term g1g2/C1C2 is commensurate with the magnitude of the other terms in the denominators of said transfer responses, thereby insuring that said transfer responses are directly controlled by the values of g1 and g2.
Claim 3
Dependent Claim
190 words
An active filter circuit comprising: first, second, and third variable transconductance amplifiers having transconductance coefficients g1, g2, and g3, respectively, each having first and second input terminals, a control terminal and an output terminal; a first capacitor having a capacitive value C1 jointly connected to said first amplifier output terminal and said second amplifier first input terminal, and to a terminal of fixed potential; a first resistor having a resistive value R2 jointly connected to said second amplifier output terminal and said third amplifier first input terminal, and to said terminal of fixed potential; a second capacitor having a capacitive value C2 connected to said second amplifier output terminal and to said terminal of fixed potential; a second resistor having a resistive value R3 jointly connected to said third amplifier output terminal and said first amplifier first input terminal, and to said terminal of fixed potential; a resistive network coupling an input signal of magnitude Alpha 1Ein, Alpha 2Ein, and Alpha 3Ein to said second input terminals of said first, second, and third amplifiers, respectively; said output terminal of said third variable transconductance amplifier providing a filter transfer response of
Claim 4
Dependent Claim
190 words
An active filter circuit comprising: first, second, and third variable transconductance amplifiers having transconductance coefficients g1, g2, and g3, respectively, each having first and second input terminals, a control terminal and an output terminal; a first capacitor having a capacitive value C1 jointly connected to said first amplifier output terminal and said second amplifier first input terminal, and to a terminal of fixed potential; a first resistor having a resistive value R2 jointly connected to said second amplifier output terminal and said third amplifier first input terminal, and to said terminal of fixed potential; a second capacitor having a capacitive value C2 connected to said second amplifier output terminal and to said terminal of fixed potential; a second resistor having a resistive value R3 jointly connected to said third amplifier output terminal and said first amplifier first input terminal, and to said terminal of fixed potential; a resistive network coupling an input signal of magnitude Alpha 1Ein, Alpha 2Ein, and Alpha 3Ein to said second input terminals of said first, second, and third amplifiers, respectively; said output terminal of said third variable transconductance amplifier providing a filter transfer response of
Claim 5
Dependent Claim
261 words
An active filter circuit comprising: first and second variable transconductance amplifiers having transconductance values g1 and g2, respectively, each amplifier having first and second input terminals, a control terminal and an output terminal; a first resistor having resistive value R1 jointly connected to said output terminal of said first amplifier and said first input terminal of said second amplifier, and to a first signal terminal, E5; a first capacitor having a capacitive value C1 connected to said first amplifier output terminal and to a second signal terminal, E1; a second capacitor having a capacitive value C2 jointly connected to an output terminal of said second amplifier and said second input terminal of said first amplifier, and to a third signal terminal, E4; a fourth signal terminal, E2, connected to said second input terminal of said second amplifier; a fifth signal terminal, E3, connected to said first input terminal of said first amplifier; said output of said first variable transconductance amplifier providing a filter transfer response of s2E1 + s (g1(E4 -E3)/C1 + E5/C1R1)+ g1g2E2/C1C2 s2 + s/C1R1 + g1g2/C1C2 where s is the complex frequency variable; and means connected to said control terminals of said amplifiers for selectively altering the transconductance of said first and second amplifiers to control and maintain the magnitude of the term g1g2/C1C2 commensurate with the magnitude of the other terms in the denominator of said filter transfer response, thereby insuring that the frequency of the poles of said transfer response is directly controlled by the values of g1 and g2 without interaction of any resistive components.
Claim 6
Dependent Claim
261 words
An active filter circuit comprising: first and second variable transconductance amplifiers having transconductance values g1 and g2, respectively, each amplifier having first and second input terminals, a control terminal and an output terminal; a first resistor having resistive value R1 jointly connected to said output terminal of said first amplifier and said first input terminal of said second amplifier, and to a first signal terminal, E5; a first capacitor having a capacitive value C1 connected to said first amplifier output terminal and to a second signal terminal, E1; a second capacitor having a capacitive value C2 jointly connected to an output terminal of said second amplifier and said second input terminal of said first amplifier, and to a third signal terminal, E4; a fourth signal terminal, E2, connected to said second input terminal of said second amplifier; a fifth signal terminal, E3, connected to said first input terminal of said first amplifier; said output of said first variable transconductance amplifier providing a filter transfer response of s2E1 + s (g1(E4 -E3)/C1 + E5/C1R1)+ g1g2E2/C1C2 s2 + s/C1R1 + g1g2/C1C2 where s is the complex frequency variable; and means connected to said control terminals of said amplifiers for selectively altering the transconductance of said first and second amplifiers to control and maintain the magnitude of the term g1g2/C1C2 commensurate with the magnitude of the other terms in the denominator of said filter transfer response, thereby insuring that the frequency of the poles of said transfer response is directly controlled by the values of g1 and g2 without interaction of any resistive components.
Claim 7
Dependent Claim
66 words
The active filter circuit as defined in claim 3 further comprising: means for connecting said first and third signal terminals to a terminal of fixed potential; a resistive network for applying an input signal to said first input terminal of said first amplifier; and means for applying said input signal jointly to said second signal terminal and to said second input terminal of said second amplifier.
Claim 8
Dependent Claim
60 words
The active filter circuit as defined in claim 3 further comprising: means for connecting said first and third signal terminals and said first input terminal of said first amplifier to a terminal of fixed potential; and a resistive network for selectively applying an input signal to said second signal terminal and to said second input terminal of said second amplifier.
Claim 9
Dependent Claim
233 words
An active filter circuit comprising: an input signal source; first and second variable transconductance amplifiers having variable transconductance g1 and g2, respectively, each amplifier having first and second input terminals, a control terminal, and an output terminal, said first amplifier first input terminal connected to said first amplifier output terminal; a first capacitor having a capacitive value C1 jointly connected to said first amplifier output terminal and said second amplifier first input terminal, and to said signal source; a second capacitor having a capacitive value C2 jointly connected to said second amplifier output terminal and said first amplifier second input terminal, and to a terminal of fixed potential; a resistive network connected to said second amplifier second input terminal and to said signal source providing a fraction, Alpha , of said signal source''s signal magnitude to said second input terminal of said second amplifier; said output terminal of said first variable transconductance amplifier providing a filter transfer response of (s2 + Alpha g1g2/C1C2/s2 + sg1/C1 + g1g2/C1C2) where s is the complex frequency variable; and means for applying control signals to said amplifier control terminals for selectively varying the transconductance of said amplifier to maintain the magnitude of g1g2/C1C2 commensurate with the other terms in the denominator of said transfer response, thereby insuring that the frequency of the poles of said transfer response is substantially controlled by the values of g1 and g2.
Claim 10
Dependent Claim
233 words
An active filter circuit comprising: an input signal source; first and second variable transconductance amplifiers having variable transconductance g1 and g2, respectively, each amplifier having first and second input terminals, a control terminal, and an output terminal, said first amplifier first input terminal connected to said first amplifier output terminal; a first capacitor having a capacitive value C1 jointly connected to said first amplifier output terminal and said second amplifier first input terminal, and to said signal source; a second capacitor having a capacitive value C2 jointly connected to said second amplifier output terminal and said first amplifier second input terminal, and to a terminal of fixed potential; a resistive network connected to said second amplifier second input terminal and to said signal source providing a fraction, Alpha , of said signal source''s signal magnitude to said second input terminal of said second amplifier; said output terminal of said first variable transconductance amplifier providing a filter transfer response of (s2 + Alpha g1g2/C1C2/s2 + sg1/C1 + g1g2/C1C2) where s is the complex frequency variable; and means for applying control signals to said amplifier control terminals for selectively varying the transconductance of said amplifier to maintain the magnitude of g1g2/C1C2 commensurate with the other terms in the denominator of said transfer response, thereby insuring that the frequency of the poles of said transfer response is substantially controlled by the values of g1 and g2.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-11 | 1977-08-13 | 1978-02-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-11 | 1981-08-13 | 1982-02-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-11 | 1985-08-13 | 1986-02-12 | $7700.00 | Window Closed / Lapsed |