Amplifying a signal using a control modulator that provides a bias resistance

According to one embodiment of the present invention, an amplifier includes an amplifying transistor coupled to a ground and operable to amplify a received signal. One or more bias components provide a bias resistance for the amplifying transistor. The one or more bias components include a control modulator coupled in series between the amplifying transistor and the ground. The control modulator receives a control signal and modulates the amplifying transistor in response to the control signal.

TECHNICAL FIELD

This invention relates generally to the field of amplifiers and more specifically to amplifying a signal using a control modulator that provides a bias resistance.

BACKGROUND

Transistor amplifiers include a transistor that increases the magnitude of an applied signal. A transistor amplifier may be biased to maintain appropriate current and voltage in the transistor. Self-biased amplifiers typically use a source resistor to provide the bias resistance. Self-biased amplifiers, however, typically require additional components to modulate the transistors. It is generally desirable to relax the requirement for additional components.

SUMMARY OF THE DISCLOSURE

In accordance with the present invention, disadvantages and problems associated with previous techniques for amplifying signals may be reduced or eliminated.

According to one embodiment of the present invention, an amplifier includes an amplifying transistor coupled to a ground and operable to amplify a received signal. One or more bias components provide a bias resistance for the amplifying transistor. The one or more bias components include a control modulator coupled in series between the amplifying transistor and the ground. The control modulator receives a control signal and modulates the amplifying transistor in response to the control signal.

Certain embodiments of the invention may provide one or more technical advantages. A technical advantage of one embodiment may be that a control modulator of an amplifier is used to modulate the amplifier and to provide a bias resistance to the amplifier. Another technical advantage of one embodiment may be that a control signal that provides instructions to the control modulator may operate with respect to ground. Thus, the voltage of the control signal is not required to be increased to the drain voltage of the amplifier. Another technical advantage of one embodiment may be that since the voltage of the control signal is not required to be increased, the amplifier may require fewer components.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1is a diagram illustrating a typical self-biased amplifier10that uses a source resistor34to provide a bias resistance for amplifier10. Amplifier10includes amplifying components20and control components24. Amplifying components20are located on an integrated circuit (IC)26, while control components24are external to integrated circuit26.

Amplifying components20amplify an input signal, and include a grounded transistor30and a stability/bias circuit32. Transistor30amplifies an input signal. Stability circuit32includes a source resistor34and a capacitor36. Source resistor34provides a bias resistance. An increase in the drain current I causes an increase in the voltage drop across source resistor34. The increase in the voltage drop causes the gate voltage Vgto decrease, which may stabilize the original increase in the drain current.

Control components24switch amplifier10from an on state to an off state and from an off state to an on state in response to a control signal. Control components24include a level shifter/inverter40and a drain modulator42. Level shifter/inverter40increases the voltage of the control signal to match drain voltage Vd. Typically, the voltage of the control signal is usually on the order of half the drain voltage Vd. Level shifter/inverter40also inverts a negative control signal to a positive control signal.

FIG. 2is a diagram illustrating one embodiment of a self-biased amplifier60that uses a control modulator80to provide a bias resistance for amplifier60. According to the illustrated embodiment, amplifier60may comprise a portion of an integrated circuit64. Integrated circuit64may refer to any suitable integrated circuit, and may comprise any suitable semiconductor material such as silicon or gallium arsenide (GaAs). According to one embodiment, integrated circuit64may comprise a monolithic microwave integrated circuit (MMIC).

According to the illustrated embodiment, amplifier60includes an amplifying transistor70, a resistor74, a capacitor76, and a control modulator80coupled as shown. Amplifying transistor70may comprise any suitable transistor operable to amplify a signal. For example, transistor30may comprise a radio frequency (RF) field effect transistor (FET).

One or more bias components of amplifier70may be used to provide a bias resistance. The bias components may placed in series with amplifying transistor70, between the source of transistor70and ground. According to one embodiment, the resistance of transistor80may be selected to provide a bias resistance for amplifier70. According to another embodiment, amplifier60may include resistor74. The resistance of resistor74and transistor80may be selected to provide the bias resistance.

Bias resistance refers to the resistance of one or more components, where the resistance generates a desired bias voltage when current flows through the components. The bias resistance allows for feedback voltage such that an increase in the drain current I causes an increase in the voltage drop across the source bias resistor. The source bias resistance may refer to the resistance of switch80or the resistance of switch80in series with resistor74. The voltage drop causes the gate voltage Vgto decrease, which may stabilize the original increase in the drain current.

In the illustrated embodiment, the bias resistance initiates a positive source voltage Vsto generate a negative gate voltage Vg. As an example, the bias resistance may be approximately less than 12 ohms, such as 2 to 10 ohms. A positive source voltage Vsof approximately 0.7 to 1.0 volts may be initiated to generate a negative gate voltage Vgof approximately −0.5 to −0.7 volts.

Capacitor76may comprise any suitable bypass capacitor having a capacitance to provide a ground for the source of transistor70, which may reduce variation of the amplified signal. For example, capacitor76may have a capacitance of approximately two to six Pico farads. Control modulator80may comprise any suitable transistor operable to modulate amplifier60. For example, control modulator80may comprise a field effect transistor operable to switch amplifier60from an on state to an off state and from an off state to an on state. Control modulator80may modulate amplifier60in response to a control signal. A control signal may refer to a signal that directs the operation of amplifier60, and may comprise any suitable signal such as a transistor-transistor logic (TTL) signal.

According to one embodiment, the control signal modulates switch80with respect to ground. Accordingly, the control signal typically is not required to be inverted or amplified. The control signal may be sent by a control system that controls the operation of the amplifier. The control system may be part of integrated circuit64, or may be external to integrated circuit64. Accordingly, control modulator80may control amplifier60without the need for the control components24of amplifier10ofFIG. 1, for example, inverter40and drain modulator42. Thus, amplifier60may use fewer components.

Modifications, additions, or omissions may be made to amplifier60without departing from the scope of the invention. For example, either control transistor80or a combination of control modulator80and resistor74may provide the bias resistance. Moreover, the components of amplifier60may be integrated or separated according to particular needs. Additionally, operations of amplifier60may be performed using any suitable logic comprising software, hardware, other logic, or any suitable combination of the preceding. As used in this document, “each” refers to each member of a set or each member of a subset of a set.

FIG. 3is a flowchart illustrating one embodiment of a method for amplifying a signal using amplifier60ofFIG. 2. The method begins at step100, where control modulator80of amplifier60receives a control signal. The control signal instructs control modulator80to turn amplifier60on. Control modulator80turns amplifier60on in response to the control signal at step104.

Drain current I may increase or decrease at step108, initiating a response in accordance with the bias resistance provided by control modulator80. Steps110through116describe the response if drain current I increases. The voltage drop across the bias resistance increases at step110in response to the increased drain current I. The gate voltage Vgdecreases in response to the increased voltage drop at step114. The drain current decreases in response to the decreased gate voltage Vgat step116. The original increase in the drain current is stabilized by the decreased gate voltage Vgat step118.

Steps120through126describe the response if drain current I decreases. The voltage drop across the bias resistance decreases at step120in response to the decreased drain current I. The gate voltage Vgincreases in response to the decreased voltage drop at step124. The drain current increases in response to the decreased gate voltage Vgat step126. The original decrease in the drain current is stabilized by the increased gate voltage Vgat step120.

Control modulator80receives another control signal at step130. The control signal instructs control modulator80to turn amplifier60off. Control modulator80turns amplifier60off in response to the control signal at step134. After turning amplifier60off, the method terminates.

Modifications, additions, or omissions may be made to the method without departing from the scope of the invention. The method may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order without departing from the scope of the invention.

Certain embodiments of the invention may provide one or more technical advantages. A technical advantage of one embodiment may be that a control modulator of an amplifier is used to modulate the amplifier and to provide a bias resistance to the amplifier. Another technical advantage of one embodiment may be that a control signal that provides instructions to the control modulator may operate with respect to ground. Thus, the voltage of the control signal is not required to be increased to the drain voltage of the amplifier. Another technical advantage of one embodiment may be that since the voltage of the control signal is not required to be increased, the amplifier may require fewer components.

While this disclosure has been described in terms of certain embodiments and generally associated methods, alterations and permutations of the embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.