JPH04237203A - Amplifier - Google Patents

Abstract

PURPOSE:To improve the leading edge characteristic at power save release by suppressing a deviation in a bias level of an output signal. CONSTITUTION:The amplifier is provided with an output transistor(TR) 2 and an output terminal of the output TR 2 is connected to a load circuit 6 via a capacitive coupling circuit 4. Moreover, a semiconductor switch element 10 is provided in a circuit 8 energizing an operating DC current to the output TR 2. Then at the intermittent reception release, a power save control signal transferring an active region of the semiconductor switch 10 to the cut-off state is applied to the semiconductor switch element 10 in the circuit 8 energizing the output TR 2. The semiconductor switch 10 supplies a leakage current depending on the cut-off state to the output TR 2. Thus, even when the amplifier is set in the power save state, a signal average DC voltage level almost required for the load circuit 6 is generated at an output terminal of the output TR 2.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention aims to reduce the output bias level to the required signal average DC voltage level when power save is released in order to improve the rise characteristics when the output is connected to a load circuit via a capacitive coupling circuit. The present invention relates to an amplifier employing the maintenance of In addition to wired communication networks, current communication networks include wireless communication networks, that is, mobile communication systems. In this mobile communication system, the mobile station (mobile radio telephone) is not always in the same service area, but usually moves between multiple service areas while talking to the other party. be. When the mobile station moves from that service area to another service area, the mobile station switches the base station (fixed station) receiving service and continues the call with the caller. A physical communication system has been established. At the time of switching, it is essential to switch the communication channel, that is, the wireless channel, in the mobile station.

[0002] Mobile stations (portable wireless telephones) generally have a much longer period of time when they are out of service than when they are constantly receiving service. During the period when the mobile station is not receiving service, the mobile station always keeps only the functional circuits capable of responding to the service in operation, and some or all of the other circuits stop functioning. The means adopted in this type of device are also adopted in mobile stations.

[0003] For each of these cases, the portable radio telephone mounted on the mobile station is provided with the above-mentioned means in order to reduce the consumption of the DC power supply mounted on the mobile station as much as possible.

0004

2. Description of the Related Art FIG. 3 shows the configuration of a conventional wireless transmitter/receiver of a mobile phone. In FIG. 3, an antenna 20, a filter 22, a receiving section 24, a transmitting section 26, a synthesizer section 28
, an intermediate frequency amplifier 30, an active filter 32, a capacitor 34, and a semiconductor switching element 31 provided in a power supply circuit that supplies operating power to the intermediate frequency amplifier 30. An active filter 32 is connected to the output of this intermediate frequency amplifier 30. The intermediate frequency amplifier 30 and active filter 32 are connected via a capacitor 34, as shown in FIG. When switched off by this simple switching signal of the semiconductor switching element 31, the active filter 3
The rise characteristics of the input signal to 2 deteriorate. Along with this, the output signal of the active filter 32 sampled at the sampling level also changes as shown in FIG. 4. During the time period T0 shown in FIG. 4, the received data cannot be received correctly.

In order to solve this problem, a rise improving circuit as shown in FIG. 5 is provided. The rise improvement circuit includes a capacitor 36 provided between the capacitor 34 and the resistor 44, a field effect transistor 38 connected in parallel with the capacitor 36, a resistor 40 connected to the gate of the field effect transistor 38, and A switching control signal is applied to the other terminal of the resistor 40, and the other terminal of the resistor 42 is grounded. The capacitance of capacitor 36 is smaller than that of capacitor 34.

[0006]

According to the rise improvement circuit described above, since the field effect transistor 38 is turned off when the switching control signal is applied, that is, during intermittent reception, the capacitor 36 is connected in series with the capacitor 34. , and the time constant becomes smaller. Therefore, it is possible to prevent the deterioration of the rise characteristics of the received signal that would otherwise occur when the semiconductor switch element 31 is simply switched off. However, not only is capacitor 36 required, but additional circuitry to effectuate the switching is also required. The present invention was created in view of the above technical problem, and an object of the present invention is to provide an amplifier that suppresses deviations in the output signal bias level and improves rise characteristics when power save is canceled.

[0007]

SUMMARY OF THE INVENTION FIG. 1 shows a block diagram of the principle of the present invention. The present invention provides an amplifier having an output transistor 2, in which the output end of the output transistor 2 is connected to a load circuit 6 via a capacitive coupling circuit 4, and a circuit 8 for supplying operating direct current to the output transistor 2. A semiconductor switch element 10 is provided in the semiconductor switch element 10, and a power save control signal that can shift from its active region to a cut-off state is applied to the switching control input of the semiconductor switch element 10 when intermittent reception is canceled. do.

[0008]

[Operation] The switching control input of the semiconductor switch 10 in the circuit 8, which energizes the output transistor 2 of the amplifier, is a power saver that can shift from the active region of the semiconductor switch 10 to a cut-off state when intermittent reception is canceled. Application of a control signal is caused. The semiconductor switch 10 allows a leakage current determined by its cut-off state to flow through the output transistor 2. Therefore, even if the amplifier is set to the power save state, the signal average DC voltage level required by the load circuit 6 is generated at the output terminal of the output transistor 2. Therefore, the average DC voltage level of the signal in the load circuit 6 when the power save state is released can be quickly recovered. In other words, the rise characteristics can be improved.

[0009]

Embodiment FIG. 2 shows an embodiment of the present invention. In this figure, a semiconductor switch element 1 is connected between the output transistor 25 and the resistor 27 of the intermediate frequency amplifier 30 in FIG.
2 is a feature of the present invention. The output terminal 29 of the intermediate frequency amplifier 14 configured in this manner is connected to the active filter 32 via a capacitor 34 as in the conventional case. The semiconductor switch element 12 is, for example, N
A power save control signal is supplied to the base of a PN type transistor. In this configuration, resistor 27 inherently exhibits high impedance, as in conventional intermediate frequency amplifier 30.

In FIG. 2, the output transistor 25 is
The active filter 32 corresponds to the output transistor 2 in FIG. 1, and the active filter 32 corresponds to the load circuit 6 in FIG. The circuit including the resistor 27 corresponds to the circuit 8 in FIG. 1, and the semiconductor switch element 12 corresponds to the semiconductor switch element 10 in FIG. By configuring the intermediate frequency amplifier 14 in this manner, the semiconductor switching element 12 is turned off during power saving, but due to the characteristics of the element, leakage current (μA) flows through the semiconductor switching element 12 even when it is off. However, a charging current also flows to the capacitor 34. Therefore, a required voltage value can be generated at the output terminal 29 of the intermediate frequency amplifier 14 even during power save, unlike when the semiconductor switch element 31 in the conventional intermediate frequency amplifier 30 is switched off. Therefore, the difference from the voltage value at the output terminal 29 (average level for data sampling) when power save is canceled can be reduced. Therefore, the time required to reach the average level, that is, the rise time can be shortened. To reduce as much as possible erroneous reception of received data during intermittent reception (
(see T0 in Figure 4).

[0011]

As explained above, according to the present invention, in intermittent reception in a mobile communication system, the output signal level of an amplifier that needs to be turned on/off can be controlled by signal sampling regardless of whether power save is switched on or off. Since the signal level (signal average level) or a level close to this can be maintained, the rise characteristics in intermittent reception can be improved. Fewer components are required to achieve this effect.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of the principle of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a configuration diagram of a portable radio telephone.

FIG. 4 is a diagram showing a conventional received signal sampling situation in a portable radio telephone.

FIG. 5 is a diagram showing an intermediate frequency signal output circuit section provided with a rise characteristic improvement circuit.

[Explanation of symbols]

2 Output transistor (output transistor 25) 6
Load circuit (active filter 32) 8 circuits (circuit including resistor 27)

Claims (1)

[Claims] 1. An amplifier comprising an output transistor (2), an output terminal of the output transistor (2) being connected to a load circuit (6) via a capacitive coupling circuit (4), wherein the output transistor ( 2) a semiconductor switching element (10) is provided in the circuit (8) for supplying an operating DC current to the switching control input of the semiconductor switching element (10); An amplifier characterized in that it receives application of a save control signal when intermittent reception is canceled.