JPH0555841A - Transistor high frequency amplifier circuit - Google Patents

Abstract

PURPOSE:To reduce the feedback capacity of a high frequency amplifying transistor(TR) and to reduce the leakage of a high frequency signal by impressing voltage to the collector electrode of the TR even when a high frequency output signal is OFF. CONSTITUTION:A high frequency signal inputted to an input terminal 1 is allowed to flow into the base of the high frequency signal amplifying TR 9 through a DC removing capacitor 2. Voltage is impressed from a DC power supply 8 to the collector terminal of the TR 9, and when a switch circuit 10 is closed, the base voltage of the TR 9 is impressed through a bias resistor 4 and the TR 9 executes amplifying operation and outputs the operated result to an output terminal 7. When the switch 10 is opened, the voltage of the power supply 8 is impressed to the collector of the TR 9. The collector voltage is set up to an area in which the base DC bias current of the TR 9 has no amplified gain by a resistor 5. By this constitution, the feedback capacity is reduced as compared with a case impressing no voltage between the base and collector of the TR 9 and the leakage of the high frequency signal can be reduced.

Description

Detailed Description of the Invention

[0001]

The present invention is used in a high frequency amplifier circuit. In particular, it relates to intermittent high frequency output signals.

[0002]

2. Description of the Related Art In a conventional transistor high frequency amplifier circuit, when a high frequency output signal is cut off, all the voltages applied to the transistors are cut off, so that the potential difference between the collector terminal and the emitter terminal becomes zero.

[0003]

In this state, the feedback capacitance between the collector and the base rises as compared with the case where a voltage is applied, so that the leakage power of the high frequency signal appearing at the output terminal becomes large.

The present invention has been made in view of such a background, and an object thereof is to provide a circuit for reducing leakage power when a high frequency output signal is disconnected in a transistor high frequency amplifier circuit.

[0005]

According to the present invention, in a transistor high frequency amplifier circuit having circuit means for connecting and disconnecting a high frequency output signal, said circuit means is a base DC of the transistor in the state where a voltage is applied to the collector electrode of the transistor. It is characterized by including a switch circuit for setting a bias current in a region where there is no amplification gain of the transistor.

The switch circuit may be a semiconductor switch circuit.

[0007]

The feedback capacitance of the transistor can be reduced by applying a voltage to the collector electrode of the transistor for high frequency amplification even when the high frequency output signal is cut off.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described with reference to FIGS.

1 and 2 are block diagrams of an embodiment of the present invention. This device is a transistor high-frequency amplifier circuit provided with circuit means for connecting and disconnecting a high-frequency output signal, wherein the circuit means applies a voltage to the collector electrode of the high-frequency signal amplifying transistor 9, and the base of the high-frequency signal amplifying transistor 9 It is characterized by including a switch circuit 10 for setting a DC bias current in a region where there is no amplification gain of the high frequency signal amplifying transistor 9.

The switch circuit 10 shown in FIG.
Can also be a semiconductor switch circuit 14 as shown in FIG.

Next, the operation of the embodiment of the present invention will be described with reference to FIGS.
Will be described.

The high frequency signal input to the high frequency signal input terminal 1 passes through the direct current removing capacitor 2 and flows into the base of the high frequency signal amplifying transistor 9. DC power supply 8
Applies a voltage to the collector terminal of the high frequency signal amplifying transistor 9, and a voltage is applied to the base of the high frequency signal amplifying transistor 9 via the bias resistor 4 when the switch circuit 10 is closed. Performs an amplifying operation. The amplified high frequency signal passes through the direct current removing capacitor 3 and is output to the high frequency output terminal 7.
Next, when the switch circuit 10 is opened, no voltage is applied to the base of the high-frequency signal amplifying transistor 9, so that the high-frequency signal output to the high-frequency output terminal 7 has a feedback capacitance between the base and collector of the high-frequency signal amplifying transistor 9. Determined by Even after the switching circuit 10 is opened to the high frequency signal amplifying transistor 9, the voltage of the DC power supply 8 passes through the bias resistor 5 and is constantly applied to the collector electrode of the high frequency signal amplifying transistor 9 during circuit operation. Therefore, since the feedback capacitance when the voltage is applied is smaller than the feedback capacitance when the voltage is not applied between the base and the collector, the leakage of the high frequency signal output to the high frequency output terminal 7 can be reduced. .

In the embodiment of the present invention, as shown in FIG. 2, the switch circuit 10 of FIG. 1 is replaced with a semiconductor switch circuit 14. By turning on / off the control signal input to the semiconductor switch circuit control signal input terminal 13, the semiconductor switch circuit transistor 11 is turned on / off to form a semiconductor switch circuit.

[0014]

EFFECTS OF THE INVENTION By constantly applying a voltage to the collector electrode of a high frequency amplifying transistor during circuit operation, the feedback capacitance of the transistor when the high frequency signal output is cut off is reduced,
It is possible to reduce leakage of high frequency signals.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram when the switch circuit of the embodiment of the present invention is configured by a semiconductor switch circuit.

[Explanation of symbols]

 1 High Frequency Signal Input Terminal 2-3 DC Removal Capacitor 4-6 Bias Resistor 7 High Frequency Output Terminal 8 DC Power Supply 9 High Frequency Signal Amplifying Transistor 10 Switch Circuit 11 Semiconductor Switch Circuit Transistor 12 Bypass Capacitor 13 Semiconductor Switch Circuit Control Signal Input Terminal 14 Semiconductor switch circuit

Claims (2)

[Claims] 1. A transistor high frequency amplifier circuit comprising circuit means for connecting and disconnecting a high frequency output signal, wherein the circuit means amplifies a base DC bias current of the transistor in a state where a voltage is applied to a collector electrode of the transistor. A transistor high-frequency amplifier circuit including a switch circuit for setting a gain-free region. 2. The transistor high frequency amplifier circuit according to claim 1, wherein the switch circuit is a semiconductor switch circuit.