JPH0572764B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a broadband high efficiency amplifier.

In recent years, wideband amplifiers for use in VHF and UHF band mobile communications and mobile phone devices have been developed. This amplifier is required to have wideband characteristics and low power consumption. Typically, this type of application uses a matched amplifier using a lossless circuit or a resistor/coupled amplifier using a resistor and coupling capacitor.
A capacitively coupled amplifier is used. However, since matching amplifiers use circuit elements whose reactances vary depending on frequency, such as lumped constant capacitors, inductors, and distributed constant lines, it is difficult to achieve a wide band, and furthermore, unstable operation such as parasitic oscillation is likely to occur. Usually, the bandwidth of a matched amplifier is limited to one to two octaves. On the other hand, in a resistor-capacitive coupling amplifier, a resistor having no frequency characteristics is used as a circuit element, so it is easy to widen the band, and parasitic oscillations are less likely to occur. However, the resistance-capacitive coupling amplifier has the disadvantage that the DC bias current and voltage are supplied through the resistor, and the power consumption of the amplifier increases significantly due to the power loss caused by the resistor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a broadband high-efficiency amplifier that eliminates the above drawbacks.

According to the present invention, a series circuit of a resistor and a DC blocking capacitor is used as an AC load, and the drain electrode (or A broadband, high-efficiency amplifier is obtained, which is characterized by supplying a DC bias current and voltage to the collector electrode).

In the present invention, since the AC load is a resistor with no frequency characteristics, it can be made wider and more compact, and the DC bias supply is performed through an inductor, which reduces unnecessary power loss, making it possible to use a wide-band, high-efficiency amplifier. realizable. In addition, in this amplifier, DC bias can be supplied through an AC load resistor instead of through the inductor, so it can be used as an amplifier that stabilizes circuit operation at the expense of power consumption. is also possible. These features are particularly effective in monolithically integrated amplifiers, which are a means of mass-producing identical circuits.

The present invention will be explained in detail below using the drawings.

Figure 1 is a diagram for explaining a conventional two-stage resistor-capacitive coupling amplifier, where a is its equivalent circuit, and b
is the AC equivalent circuit for the first stage FET, c is the first stage
This is the DC equivalent circuit for FET. Figure 1a
A series circuit of R _L and C _B is connected in parallel to the drain electrode 2 of the first stage FET whose source electrode 3 is grounded, and a bias supply terminal 7 is provided between R _L and C _B. A coupling capacitor C _C is connected between the drain electrode 2 and the subsequent FET gate electrode 5.
is provided, and a bias voltage is applied to the gate electrode 5 through R _G having a resistance value of several kΩ.
The source electrode 6 of the latter stage FET is grounded. 1
4 is the gate electrode of the front-stage FET, and 4 is the drain electrode of the rear-stage transistor. Since the input impedance of R _G and FET is sufficiently higher than R _L , the first stage
The AC equivalent circuit for FET is shown in Figure 1b. Furthermore, the DC equivalent circuit becomes as shown in Figure 1c.

In Figure 2-c, the power consumed by R _L is
If the current flowing through R _L is I _D , then R _L I _2D .

Figure 2 shows an embodiment of the present invention.
FIG. 2 is a diagram for explaining a wideband, high-efficiency amplifier with a two-stage FET configuration. In the figure, the drain electrode 12 of the FET whose source electrode 13 is grounded has R _L and C _B
series circuits are provided in parallel, and the other end of an inductor L _B having a bias supply terminal at one end is connected. The drain electrode 12 and the subsequent stage
A coupling capacitor C _C is connected between the FET gate electrodes 15.
is provided, and a gate bias voltage is supplied to the gate electrode 15 from a terminal 18 through a high resistance _RG . A second terminal for supplying drain bias to the first stage FET is provided between R _L and C _B. 1
1 is the gate electrode of the first stage FET, and 14 and 16 are the drain electrode and source electrode of the second stage FET, respectively. Since the input impedances of L _B , L _G and the subsequent FET are sufficiently high compared to R _L , Fig. 2a
The AC equivalent circuit of the circuit is as shown in Fig. 2b. The DC equivalent circuit is as shown in Figure 2c.

In the amplifier of the embodiment shown in FIG. 2, DC bias is supplied through the inductor, so no DC power is consumed outside the FET. Therefore, in the amplifier of this example, the first stage circuit alone has a lower power consumption than the conventional amplifier.
It is possible to reduce power consumption by I ² R _L. Note that the amplifier of this embodiment has a second bias supply terminal 19.
, it is possible to supply bias through the resistor R _L , and it is also possible to use it as a stable amplifier that is less likely to cause parasitic oscillations at the expense of efficiency.

FIG. 3 is a circuit configuration diagram when the amplifier of the embodiment of FIG. 2 is made into a monolithic structure. In the figure, components 11 to 19 are the same components as in FIG. 2 and are indicated by the same symbols. R _G , C _C , C _B
also shows the same thing as Figure 2. 21 is capacitor
C _B is a bonding pad for grounding, 22 is a lower electrode of capacitor C _C , and 23 is a dielectric film. The shaded area in the figure is an n-type channel formed by ion implantation, and 24 is a semi-insulating GaAs substrate. 12, 13, 14, 16, 22, and 25 are made of ohmic metal, and 11 and 15 are made of shot key metal. In the embodiment amplifier of FIG. 3, an external inductor L _B is connected to 12, and a drain bias is supplied through L _B , thereby reducing power consumption. It is also possible to supply a drain bias through the resistor R _L by applying a DC voltage to 19, and it is also possible to achieve high stability at the expense of power consumption. The circuit of FIG. 3 incorporates these functions into one monolithic integrated circuit.

According to the present invention, since the AC load is a resistor and the DC bias is supplied through an inductor, a compact, wideband, and highly efficient amplifier can be realized. Furthermore, in the present invention, since DC bias can be supplied through an AC load resistor without going through the inductor, it is also possible to use it as a highly stable operation amplifier at the expense of power consumption, especially when mass-producing the same circuit. This has great effect in some monolithically integrated amplifiers.

Note that although GaAs was used as the semiconductor substrate in the monolithic amplifier of the embodiment shown in FIG.
It is not limited to GaAs, but may be Si, InP, etc.

[Brief explanation of drawings]

FIG. 1 shows a conventional wideband amplifier, FIG. 2 shows a wideband amplifier according to an embodiment of the present invention, and FIG. 3 shows an example of a monolithic configuration of the amplifier of the embodiment shown in FIG. In Fig. 1, 1 and 5 are FET gate electrodes, 3,
6 is a source electrode, 2 and 4 are drain electrodes, 7 is a drain bias supply terminal, 8 is a gate bias supply terminal, R _L and _RG are resistors, and C _B and C _C are capacitors. In FIG. 2, 11 and 15 are FET gate electrodes, 13 and 16 are source electrodes, 12 and 14 are drain electrodes, 17 and 19 are bias supply terminals,
R _L and R _G are resistors, C _B and C _C are capacitors, and L _B is an inductor. In FIG. 3, the shaded area is an n-type channel, 24 is a semi-insulating GaAs substrate, and 23 is a dielectric film.

Claims (1)

[Claims] 1 A series circuit of a resistor and a DC blocking capacitor is used as an AC load, and a DC bias is applied directly to the drain electrode (or collector electrode) of the amplification transistor through an inductor that has a sufficiently higher impedance than the resistor even at the bottom of the amplification band. Wideband high efficiency amplifier characterized by supplying current and voltage.