US3641452A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pi-coupled low-noise amplifier
Assignee: Individual
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Filing: 1970-07-02
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Granted: 1972-02-08
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Expires: 1990-07-02
Abstract
Abstract Two stages of a series cascade amplifier are coupled by a Pi network. The amplifier stages may be grounded grid in the case of vacuum tube or grounded gate where the stages are field effect transistors. The Pi network coupling, cooperating with the stages in a stable grounded grid or grounded gate configurations allows the impedance of the Pi network to be adjusted for lowest noise with immunity from oscillation.
Inventors
- 👤 Willie L Steed
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:24
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/189; H03F3/19; H03F3/193; H03F3/1935; H03F1/00; H03F1/26; H03F1/28; H03F2200/00; H03F2200/372
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
274 words
A Pi-coupled low-noise amplifier comprising: a variable impedance means; means to receive an input signal; a load connecting means; a first valve means having an input means, an output means and a control means; a first and second impedance means; said input means of said first valve means connected to said signal-receiving means, said output means of said first valve means connected to said variable impedance; said first impedance means connected between said input means and said control means of said first valve means and biasing said control means whereby the output of said first valve means is responsive to the signal received by said receiving means; a second valve means having an input means, an output means and a control means; said variable impedance means being connected to said input means of said second valve means at an end of said variable impedance opposite the end connected to said first valve means; said output means of said second valve means connected to said load-connecting means and said second impedance means connected between said input means and said control means of said second valve means and biasing said control means whereby the output of said second valve means is responsible to the signal at the output means of said first valve means; a first and second RF bypass means connected between said control means of said first and second valve means respectively and ground; and said bypass means connecting said control means to ground at the signal frequency and isolating the control means from ground and frequencies below RF whereby the variable impedance means can be adjusted for minimum noise without incurring feedback isolation.
Claim 2
Dependent Claim
274 words
A Pi-coupled low-noise amplifier comprising: a variable impedance means; means to receive an input signal; a load connecting means; a first valve means having an input means, an output means and a control means; a first and second impedance means; said input means of said first valve means connected to said signal-receiving means, said output means of said first valve means connected to said variable impedance; said first impedance means connected between said input means and said control means of said first valve means and biasing said control means whereby the output of said first valve means is responsive to the signal received by said receiving means; a second valve means having an input means, an output means and a control means; said variable impedance means being connected to said input means of said second valve means at an end of said variable impedance opposite the end connected to said first valve means; said output means of said second valve means connected to said load-connecting means and said second impedance means connected between said input means and said control means of said second valve means and biasing said control means whereby the output of said second valve means is responsible to the signal at the output means of said first valve means; a first and second RF bypass means connected between said control means of said first and second valve means respectively and ground; and said bypass means connecting said control means to ground at the signal frequency and isolating the control means from ground and frequencies below RF whereby the variable impedance means can be adjusted for minimum noise without incurring feedback isolation.
Claim 3
Dependent Claim
245 words
The Pi-coupled amplifier of claim 1 wherein said variable impedance is a variable inductance, said first valve means being a vacuum tube having a grid, cathode and plate, said input means being the cathode, said control means being the grid and said output means being the plate; said second valve means being a vacuum tube having a cathode grid and plate, said input means being the cathode, said control means being the grid, said output means being the plate; said variable impedance means is a variable inductance and is connected between the plate of said first vacuum tube and the cathode of said second vacuum tube; said first impedance means is a resistance connected between said cathode of said first vacuum tube and said grid of said first vacuum tube; said resistance biasing said first vacuum tube in response to the input signal; said second impedance means is a resistance connected between said cathode and said grid of said second vacuum tube, said resistance biasing said grid of said second vacuum tube in response to the output of said first vacuum tube, said output means including a variable inductance and a coupling coil connected to a load, said variable inductance and said coupling coil cooperating to form a transformer at said signal frequency; and said receiving means being a parallel tuned resonant tuned circuit including an inductance and variable capacitance which cooperates with said indUctance to form a parallel resonance circuit at said signal frequency.
Claim 4
Dependent Claim
197 words
The Pi-coupled amplifier of claim 1 wherein said first valve means is a first field effect transistor having a collector, gate and source, said collector being the output means, said gate being the control means and said source being the input means, said source connected to said receiving means, said gate responsive to said input signal and controlling the output of said first field effect transistor, said collector of said first field effect transistor connected to said variable impedance means; and said second valve means is a second field effect transistor, said second field effect transistor having a source gate and collector, said source being the input means, said gate being the control means and said collector being the output means, said source of said second field effect transistor connected to said series impedance means at the side of said impedance means opposite the said side connected to said collector of said first field effect transistor; and said gate of said second field effect transistor controlling said second field effect transistor output in response to the output of said first field effect transistor; said second field effect transistor having the collector connected to a load connecting means.
Claim 5
Dependent Claim
26 words
The Pi-coupled amplifier of claim 2 wherein said first and second vacuum tube is connected in series with said power supply at DC and signal frequencies.
Claim 6
Dependent Claim
28 words
The Pi-coupled amplifier of claim 2 wherein said first and second vacuum tubes are connected in parallel with said DC power supply and in series with the signal.
Claim 7
Dependent Claim
21 words
The Pi-coupled amplifier of claim 3 wherein said field effect transistors are connected in series with said power supply at DC.
Claim 8
Dependent Claim
123 words
The Pi-coupled amplifier of claim 3 wherein said input means is a parallel tuned circuit including an inductance and a variable tuned capacitor; said source of said first field effect transistor is connected to said receiving means; said first impedance means is a resistance; said collector of said first field effect transistor is connected to said variable impedance means; said source of said second field effect transistor is connected to said variable impedance means at the side opposite the connector to said connector of said first field effect transistor; said second impedance means is a resistance; and said output means includes a second variable inductance and a coupling coil inductively coupled to said second variable inductance forming a transformer at said signal frequency.
Claim 9
Dependent Claim
29 words
The Pi-coupled amplifier of claim 3 wherein said first and second field effect transistors are connected in parallel with said DC power supply and in series with the signal.
Claim 10
Dependent Claim
162 words
A Pi-coupled low-noise amplifier comprising: at least two successive stages of amplification, each stage having an input and an output; bias means for each stage; a variable impedance means, said variable impedance means connected at one end to the output of a first one of the amplifier stages and connected at its other end to the input of a second and successive state of amplification and operatively connecting the two successive states of amplification; each said amplification stage having a control element, controlling the output of its respective stages in response to a signal impressed on the control element, through said bias means; and a first and second RF bypass means connected between each said control means and ground respectively, and isolating said control means from ground at frequencies below RF whereby said variable impedance means may be adjusted for saturated amplifier operation without incurring feedback oscillation through capacitive coupling between any of the input, output or control elements of each stage.
Claim 11
Dependent Claim
162 words
A Pi-coupled low-noise amplifier comprising: at least two successive stages of amplification, each stage having an input and an output; bias means for each stage; a variable impedance means, said variable impedance means connected at one end to the output of a first one of the amplifier stages and connected at its other end to the input of a second and successive state of amplification and operatively connecting the two successive states of amplification; each said amplification stage having a control element, controlling the output of its respective stages in response to a signal impressed on the control element, through said bias means; and a first and second RF bypass means connected between each said control means and ground respectively, and isolating said control means from ground at frequencies below RF whereby said variable impedance means may be adjusted for saturated amplifier operation without incurring feedback oscillation through capacitive coupling between any of the input, output or control elements of each stage.
Claim 12
Dependent Claim
243 words
A Pi-coupled low-noise amplifier comprising: at least two successive stages of amplification, each stage having an input and an output; a variable impedance means, said variable impedance means connected at one end to the output of the first of said successive amplifier stages and connected at its other end to the input of the second successive state of amplification and operatively connecting the output of said first stage to the input of said second stage; each said amplification stage having a control element, controlling the output of its respective stage in response to a signal impressed on the control element; the input of the first one of said successive stages connected directly to an input signal; an impedance means connected between the input and the control element of said first stage whereby the impedance means biases the control element in response to said input signal; an impedance means connected between the input and the control element of said second stage whereby the impedance means biases the control element in response to the signal at the output of said first stage; and a first and second RF bypass means connected to said control element of the first and second stages, respectively, and connecting said control elements to ground at RF frequencies and isolating the control element from ground to frequency less than RF whereby said variable impedance can be adjusted for lowest noise at the outputs of said amplifier stages without incurring feedback instability.
Claim 13
Dependent Claim
243 words
A Pi-coupled low-noise amplifier comprising: at least two successive stages of amplification, each stage having an input and an output; a variable impedance means, said variable impedance means connected at one end to the output of the first of said successive amplifier stages and connected at its other end to the input of the second successive state of amplification and operatively connecting the output of said first stage to the input of said second stage; each said amplification stage having a control element, controlling the output of its respective stage in response to a signal impressed on the control element; the input of the first one of said successive stages connected directly to an input signal; an impedance means connected between the input and the control element of said first stage whereby the impedance means biases the control element in response to said input signal; an impedance means connected between the input and the control element of said second stage whereby the impedance means biases the control element in response to the signal at the output of said first stage; and a first and second RF bypass means connected to said control element of the first and second stages, respectively, and connecting said control elements to ground at RF frequencies and isolating the control element from ground to frequency less than RF whereby said variable impedance can be adjusted for lowest noise at the outputs of said amplifier stages without incurring feedback instability.
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) | 1975-02-07 | 1975-08-09 | 1976-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-02-07 | 1979-08-09 | 1980-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-02-07 | 1983-08-09 | 1984-02-08 | $7700.00 | Window Closed / Lapsed |