JPH05327358A - Amplifier circuit for transmission - Google Patents

Abstract

PURPOSE:To increase output power with a low power supply voltage by directly connecting a power supply terminal to a collector at the time of operating a transistor by performing control by providing a switch part at the base of this transistor. CONSTITUTION:Among a pair of power supply terminals, the collector side terminal of a transistor(Tr) Q11 is used as a first power supply terminal P and the emitter side terminal is used as a second power supply terminal G. At the time of (operations) closing a switch part 11, a current to be supplied from the terminal P through a first resistor R11 and a current to be supplied from the terminal G through a second resistor R12 are turned to the bias current of the Tr Q11 and with this current, the amplifying operation is performed. At the time of opening (stopping) the switch part 11, the base of the Tr Q11 is only connected through the resistor R12 to the terminal G, and the potential is made equal to that of the terminal G. Therefore, no current flows to the Tr Q11, and the amplifying operation is stopped. Thus, the circuit is operated with the low voltage of a dry battery or the like, and the output power of the amplifier for transmission can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission amplifier circuit that operates by electric power supplied from a low-voltage power source such as a battery, such as a transmission amplifier circuit used in a cordless telephone handset.

[0002]

2. Description of the Related Art A transmission amplifier circuit used in a device operating with a battery as a power source, such as a cordless telephone handset, has a long continuous use time by avoiding unnecessary consumption of the battery. The circuit configuration shown in is used. In this circuit, a current is supplied to the collector of a transistor Q92 for power amplification through the transistor Q91, and the transistor Q91 is turned on by giving an L level to the control terminal C91 during transmission. Therefore, the transistor Q92 operates by the current supplied from the collector of the transistor Q91, and amplifies the signal given from the input terminal C92. The amplified signal is then coupled to the coupling capacitor C91,
It is transmitted from the antenna 92 via the bandpass filter 91. When not transmitting, the transistor Q91 is turned off by applying the H level (voltage equal to the positive power source P91) to the control terminal C91, and the current value flowing in the transistor Q92, which consumes a large amount of current, is set to 0. The current consumption is being reduced.

[0003]

However, when the above configuration is used, the collector-emitter voltage of the transistor Q91 is V91, the collector-emitter voltage of the transistor Q92 is V92, the emitter voltage of the transistor Q92 is V93, and the voltage of the positive power supply P91 is V94 = V94 + V94 + V92 + V93 + V92 + V93 + V93 + V93 + V93 + V93 + V92 + V93 Will be shown. This is a transistor
Q92 means operating at a voltage lower than the voltage V94 of the positive power supply P91. On the other hand, the voltage of the positive power source P91 is low because a battery is used as the power source of the cordless telephone handset, and the transistor Q92 that operates at a voltage lower than this low voltage is used.
Had a problem that its output power could not be increased.

The present invention was devised to solve the above problems, and an object thereof is to provide a transmission amplifier circuit capable of increasing output power without increasing the power supply voltage.

[0005]

In order to solve the above-mentioned problems, the transmitting amplifier circuit of the present invention has a power supply terminal on the side to which a collector of a transistor is connected, out of a pair of power supply terminals of a power supply. When the power supply terminal on the side to which the emitter of the transistor is connected is the second power supply terminal, one of the terminals is connected to the base of the transistor.
And a switch portion in which one terminal thereof is connected to the other terminal of the first resistor and the other terminal is connected to the first power supply terminal, and one terminal thereof is connected to the base, A second terminal in which the other terminal is connected to the second power terminal
The resistance of the transistor is used, and the operation of the transistor is controlled by controlling the opening and closing of the switch portion.

[0006]

When the switch section is closed, a bias current based on the current supplied from the first terminal through the first resistor and the current supplied from the second terminal through the second resistor is generated. The transistor performs an amplifying operation. Further, when the switch portion is opened, the base of the transistor is only connected to the second power supply terminal via the second resistor, so that the potential becomes equal to the potential of the second power supply terminal. Therefore, the base current stops flowing in the transistor, and the transistor is cut off, so that the amplification operation is stopped.

[0007]

1 is a circuit diagram showing an electrical connection of an embodiment in which a transmission amplifier circuit according to the present invention is applied to a cordless telephone handset.

In the figure, the base of the transistor Q11 for amplifying the power of the signal supplied from the input terminal C12 is
To supply the bias current to the transistor Q11, the first
Is connected to one terminal of the resistor R11 and one terminal of the second resistor R12, and the other terminal of the second resistor R12 is
The second power supply terminal G is connected to the ground level. The other terminal of the first resistor R11 is connected to the switch unit 11
It is connected to the collector of transistor Q12 which is one terminal.

The emitter of the transistor Q12, which is the other terminal of the switch section 11, is connected to the first power supply terminal P which is a positive power supply, and the resistor R14 is connected between the emitter and base of the transistor Q12. ing. Further, the control terminal C11 is led to the base of the transistor Q12 via the resistor R15.

The emitter of the transistor Q11 is connected to one terminal of an emitter resistor R13, and the other terminal of the emitter resistor R13 is connected to a second power supply terminal G. The emitter is also grounded via the bypass capacitor C14 (connected to the second power supply terminal G).

The collector of the transistor Q11 is connected to one terminal of a parallel tuning circuit which is composed of an inductor L11 and a capacitor C12 and tunes to the transmission frequency. The other terminal of the parallel tuning circuit is the first terminal. Of the power supply terminal P and is grounded via the bypass capacitor C11 (connected to the second power supply terminal G).

The collector of the transistor Q11 is transmitted through the coupling capacitor C13 and the band pass filter 13 that passes only the signal of the transmission frequency, thereby transmitting the power-amplified signal.
(The ground terminal of the bandpass filter 13 is connected to the second power supply terminal G).

The block 11 composed of the transistor Q12 and the resistors R14 and R15 is a block corresponding to the switch section described in claim 1.

The operation of one embodiment of the present invention having the above configuration will be described below. When there is no incoming or outgoing call and no transmission is required, the control terminal C11 is supplied with H level (voltage substantially equal to the first power supply terminal P).

At this time, the base voltage of the transistor Q12 becomes equal to the voltage of the first power supply terminal P, and the base current stops flowing, so that the transistor Q12 is cut off. As a result, the base of the transistor Q11 becomes equal to the state of being grounded via the second resistor R12, and the base current stops flowing. Therefore, transistor Q11 is
As in the case of 2, the cutoff state is set and the amplification is stopped. In other words, it is in a standby state that avoids battery consumption.

When it is necessary to transmit in order to perform an incoming call response or an outgoing call operation in this standby state, the control terminal C11
Is given an L level. At this time, transistor Q12
A current (base current) flowing to the control terminal C11 through the resistor R15 flows to the base of the transistor Q1.
2 is turned on.

Therefore, the current supplied from the collector of the transistor Q12 flows to the base of the transistor Q11 and the second resistor R12 via the first resistor R11. That is, the transistor Q11 enters the operating state because the bias current is supplied.

In this state, the transistor Q11 amplifies the high frequency signal supplied through the input terminal C12 by using the parallel tuning circuit including the inductor L11 and the capacitor C12 as the load impedance. Therefore, the power-amplified signal is guided to the bandpass filter 13 via the coupling capacitor C13 to remove unnecessary components, and then guided to the antenna 12 for transmission.

When this operation is performed, the collector of the transistor Q11 is given a voltage equal to the first power supply terminal P, ignoring the voltage drop of the inductor L11. Therefore, the operating voltage is lost to the power supply. There is no voltage.

The present invention is not limited to the above-described embodiment, and the connection of the transistors has been described as the case where the emitter is grounded. However, as for the other connection, the same applies to the case of a circuit configuration for performing amplification by grounding the base. It is possible to apply.

The transistor has been described as an NPN transistor, but it can be similarly applied to a PNP transistor.

In the above embodiment, the case where the present invention is applied to the cordless telephone handset is explained. However, the present invention can be applied to any other device that operates at a low power supply voltage, such as a transceiver.

[0023]

In the transmitting amplifier circuit according to the present invention, the base of the transistor is connected to the second power supply terminal via the second resistance, and the first power supply terminal is connected to the switch section and the first resistance. Since the configuration is such that the operation of the transistor is controlled by connecting to the base of the transistor through and controlling the opening / closing of the switch section, the collector of the transistor is directly connected to the first power supply terminal. In addition to the effect that it is possible to increase the output power without increasing the power supply voltage, the switch section needs only to control the current flowing through the first resistor in controlling the operation of the transistor. It also has the effect of enabling miniaturization of the transistors that form the switch section.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an electrical connection of an embodiment when a transmission amplifier circuit according to the present invention is applied to a cordless telephone handset.

FIG. 2 is a circuit diagram showing a conventional electrical connection.

[Explanation of symbols]

 11 Switch section Q11 Transistor R11 First resistor R12 Second resistor P First power supply terminal G Second power supply terminal

Claims (1)

[Claims] 1. A power supply terminal of a pair of power supply terminals to which a collector of a transistor is connected is a first power supply terminal, and a power supply terminal to which an emitter of the transistor is connected is a second power supply terminal. When it is used as a terminal, one terminal thereof is connected to a first resistor connected to the base of the transistor, and one terminal thereof is connected to the other terminal of the first resistor,
A switch unit having the other terminal connected to the first power supply terminal; and a second resistor having one terminal connected to the base and the other terminal connected to the second power supply terminal. An amplifier circuit for transmission, characterized in that the operation of the transistor is controlled by controlling opening / closing of the switch section.