JPH036110A - semiconductor amplifier circuit - Google Patents

Abstract

PURPOSE:To reduce output fluctuation against the fluctuation of a temperature and a source voltage, etc., by adding the control voltage of an automatic power control circuit of current detection type on the base of a transistor for amplification. CONSTITUTION:A reference voltage is generated by connecting plural diodes 3-5 in a forward direction, and keeping their currents constant with a constant current source circuit 6. Potential difference between a power source terminal 20 and the base of a PNP TR 14 is the sum of voltage drop at a resistor 2 for current detection and the voltage between the emitter and the base of the TR 14, and it is equal to the sum of the forward direction voltage of a diode 7 and the saturation voltage of a TR 8 and the voltage drop at a resistor 11 for voltage division. When the collector current of a TR 1 is increased due to the dispersion of the DC current amplification factor of the TR 1, the fluctuation of the source voltage, and temperature change, etc., the voltage drop at a resistor 2 is increased, and since the reference voltage is nearly constant, the voltage between the emitter and the base of the TR 14 is decreased, and the base current of the TR 1 supplied via a resistor 15 is reduced, which keeps its output constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor amplifier circuit used in wireless communication equipment and the like.

2. Description of the Related Art A normally operating amplification type circuit is used as an amplification circuit using a semiconductor integrated circuit. However, if the output power is large and low power consumption is required, it is necessary to use an emitter grounded amplifier circuit. A conventional amplifier circuit will be described below with reference to FIG.

In FIG. 4, 400 is a semiconductor amplification transistor;
401 and 402 are base bias resistors, 403 is an emitter resistor, 404 is a common emitter capacitor, 406 is a collector resistor, 406 is a bypass capacitor for blocking signal components, 407 is a power supply terminal, 40B is a grounding section, 409 is an input signal, and 41
0 is the amplified output signal.

There is no need to explain the circuit operation in the above configuration, which is a basic circuit for obtaining the amplification effect of a well-known transistor. Especially when such an amplifier circuit is constructed as a semiconductor integrated circuit, a large capacitance value cannot be obtained, so the grounding effect due to the common emitter capacitor 404, the bypass effect due to the bypass capacitor 406, and the loss of signal components due to the resistor 406 are reduced. , input/output matching of the semiconductor amplifying transistor 400, etc. becomes a problem. Further, when the emitter is directly grounded, the effect of grounding the emitter is improved, but the flowing current changes greatly due to variations in the DC amplification factor of the transistor 400.

As another example, a conventional circuit used particularly in a power amplifier circuit to obtain a stable output against fluctuations in voltage, temperature, etc. will be described below with reference to FIG.

In FIG. 6, 601 is an amplification transistor, 602
503 is a detection current control PNP transistor that controls the collector current of the preamplifier 502; 604 is a diode; 606 is a detection current control PNP transistor 5;
03 is a variable resistor that sets the base bias, 506 is a diode, 507 is a Zener diode, 608 is a resistor that limits the current, 509 is a diode 504, 506
, a variable resistor 606, a resistor for setting the current flowing through the Zener diode 507, 510 a current detection resistor,
611 is an inductor that blocks high frequency signal components; 612
is a capacitance, 513 and 514 are coupling capacitances, 616 is a base bias terminal for setting the base bias of the amplification transistor 6010, and 616 is a power supply terminal.

The operation of the above configuration will be explained below.

When the base voltage of the detection current control PNP transistor 603 is set by the variable resistor 6o6, if the collector current of the amplification transistor 601 increases due to fluctuations in the power supply voltage or temperature changes, and the output increases, the current detection The voltage drop due to the resistor 610 increases, and the voltage drop between the power supply terminal 616 and the PNP type transistor 60 for controlling the detection current increases.
3 becomes equal to the voltage determined by the diode 604 and the variable resistor 606.

As a result, the emitter-base voltage of the detection current control PNP transistor 603 decreases, reducing the collector current of the preamplifier 602, which reduces the output of the preamplifier 502, reduces the input power to the amplification transistor 5010, and reduces the output power. moves in the direction where is constant. When the collector current of the amplifying transistor 501 decreases, the operation is opposite to the case where the collector current increases, and the output of the pre-stage amplifier 602 is increased to operate in a constant output direction. Such a current detection type automatic power control circuit is used in a high frequency power amplification circuit, and takes the form of controlling the output power of the preamplifier 502.

Problems to be Solved by the Invention However, in the configuration of the semiconductor amplifier circuit as described above, the emitter of the amplification transistor 601 in particular is insufficiently grounded, making it impossible to obtain the output power and gain that should be obtained, and furthermore, the emitter cannot be directly connected to the ground. When grounded, there is a problem in that the current and output of the semiconductor amplification transistor vary greatly due to variations in the direct current amplification factor of the semiconductor amplification transistor 501, as well as variations in component element values and temperature characteristics. Therefore, there was a problem in that an amplifier circuit capable of obtaining large output and low power consumption could not be realized using a semiconductor integrated circuit.

The present invention solves the above-mentioned problems by realizing an amplifier circuit using a semiconductor integrated circuit that can increase output power and consume less power, and outputs power regardless of fluctuations in temperature, power supply voltage, DC current amplification factor, load impedance, etc. It is an object of the present invention to provide a semiconductor amplifier circuit equipped with a current detection type automatic power control circuit with small fluctuations.

Means for Solving the Problems The present invention directly grounds the emitter of a semiconductor amplification transistor, uses the saturation voltage of the transistor in a part of the current detection loop mainly to correct the DC amplification factor, and also uses the saturation voltage of the transistor as a reference voltage. The above object is achieved by providing a current detection automatic power control circuit using a plurality of diodes and a constant current circuit, and applying the control voltage to the base of the semiconductor amplification transistor itself.

According to the above configuration, the present invention improves temperature characteristics by using the saturation voltage of a transistor with little temperature change in the current detection loop, and uses a plurality of diodes to keep the voltage drop between the terminals constant using a constant current power supply. A constant comparison reference voltage is created in the semiconductor integrated circuit with respect to power supply voltage fluctuations, and a current detection resistor is used to detect fluctuations in the collector current of the semiconductor amplification transistor, and the current is detected between the emitter and base of the PNP transistor for current control. By changing the voltage and supplying the collector output control current to the base bias current of the semiconductor amplification transistor itself, it is possible to reduce
It has the effect of keeping the current flowing through the semiconductor amplification transistor constant against changes in temperature, load impedance, etc. and reducing output fluctuations.

EXAMPLE A first example of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a semiconductor amplifier circuit according to a first embodiment of the present invention. In Fig. 1, 1 is a semiconductor amplification transistor, 2 is a current detection resistor, 3 to 6 are multiple forward diodes, 6 is a constant current source circuit, 7 is a diode, and 8 is for utilizing saturation voltage. saturation transistor, 9
is the base resistance of the transistor 8, 10 is a diode, 11.12 is a voltage dividing resistor, 13 is a current limiting resistor, 14 is a PNP transistor for detecting current control, 16 is a resistor for supplying the control output, 16- A matching circuit 18 matches the output of the semiconductor amplifying transistor 1, the matching circuit 16 also serves as a bias supply, and the matching circuit 17
also has the function of blocking signal components, and the matching circuit 18 performs other matching. Further, 2o is a power supply, 21 is a ground, 22 is a power supply for a constant current source circuit, 23 is an input signal of the semiconductor transistor 1, 24 is its collector output, 26 is an amplified output signal, and 26 is a semiconductor integrated circuit portion.

The operation of the above configuration will be explained below. First, a Zener diode is normally used to obtain a constant terminal voltage even when the power supply voltage fluctuates and use it as a reference voltage, but in this embodiment, since it is configured with a semiconductor integrated circuit, multiple diodes 6 are connected in the forward direction, and the current flowing there is kept constant by a constant current source circuit 6 to create a reference voltage.

Here, the potential difference between the power supply terminal 2o and the base of the detected current control PNP transistor 140 is the voltage drop at the current detection resistor 2 and the detected current control PNP transistor 14.
It is the sum of the emitter-base voltages of , which is equal to the sum of the forward voltage of the diode 7 , the saturation voltage of the saturation transistor 8 , and the voltage drop across the voltage dividing resistor 11 . Note that the base bias of the saturated transistor 80 is supplied from the power supply terminal 20 by the resistor 9, and the sum of its saturation voltage and the voltage drop across the resistor 11 and 12 is equal to the voltage drop across the diode 10.
Further, the resistor 13 limits the current flowing through these circuits provided in parallel with the reference voltage.

When the collector current of the amplification transistor 1 increases due to variations in the DC current amplification factor of the semiconductor amplification transistor 1, fluctuations in the power supply voltage, temperature changes, or fluctuations in the load impedance, the voltage drop across the current detection resistor 2 increases. Since the reference voltage is approximately constant, the emitter-base voltage of the detection current control pNp transistor 14 decreases, and the base current of the semiconductor amplification transistor 10 supplied through the resistor 16 decreases. Since it operates in the direction of keeping the output constant, a current detection type automatic power control circuit using a semiconductor integrated circuit has been constructed.

The diode 7 is connected to the emitter of the PNP transistor 14.
The saturation transistor 8 is provided as a part of the current detection loop by taking advantage of the fact that it is provided so as to almost cancel out the temperature characteristics between the bases, and that the saturation voltage changes little with respect to temperature changes. Matching of the output of the semiconductor amplifying transistor 1 is achieved by an inductor 16 which also serves as a bias supply, a capacitor 17 which functions to target a signal component, and a matching circuit 18, and an amplified output signal is obtained from a terminal 26. The constant current source circuit 6 includes, for example, a Wilson current mirror circuit shown in FIG. 3(a), a three-transistor current mirror circuit shown in FIG. 22 may be connected to the power supply terminal 20 or may be separate.

When the collector current of the semiconductor amplification transistor 1 decreases, it operates in the direction of keeping the output constant, which is the opposite of the operation when the collector current increases.

As described above, according to this embodiment, the current detection type automatic circuit uses the saturation voltage of the transistor 8 as part of the current detection loop, and also uses a plurality of diodes 3 to 6 and the constant current circuit 6 for the reference voltage. By providing a power control circuit and applying its control voltage to the base of the semiconductor amplification transistor 10, the semiconductor amplification circuit can be used particularly against fluctuations in the DC current amplification factor of the transistor, as well as fluctuations in power supply voltage, temperature, or load impedance. The current flowing through the amplification transistor 1 can be kept constant and output fluctuations can be reduced, and the amplification circuit can be configured with a semiconductor integrated circuit using a grounded emitter amplification circuit, which can increase output power and reduce power consumption. , low power consumption, and low cost.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a circuit diagram of a semiconductor amplifier circuit according to a second embodiment of the present invention. In FIG. 2, three points differ from the configuration of the first embodiment. First, the saturation transistor 8 is not provided in parallel with the diode 1° as in FIG. 1, but is provided in series with the diode 7. Then, a diode 1o is connected in series with the diode 10, and the voltage between the terminals of the diode 10 is controlled by a resistor 1o.
1.12. Furthermore, as a second point, instead of directly connecting the collector of the semiconductor amplification transistor 1 and the emitter of the detection current control PNP transistor as shown in FIG. 1, the emitter output terminal 32 of the PNP transistor is connected. 2 current detection resistors are provided between the terminal 32 and the power supply terminal, and a capacitor 1 is provided between the terminal 32 and the ground.
7. An inductor 16 is provided between the terminal 32 and the collector output terminal 24 of the semiconductor amplification transistor 1. Also, as the third fish, P for detection current detection.
An NPN transistor is connected to the collector output of the NP transistor 14 for DC amplification, and the output is supplied from the resistor 31 to the base of the semiconductor amplification transistor 1.

Since the above configuration is almost the same as the first embodiment, only the differences in operation and effects will be explained.

First, if the position of the saturation transistor 8 in the current detection loop is changed as shown in Fig. 2, the temperature compensation characteristics of the current detection loop will change, so depending on the temperature characteristics of other parts, this embodiment will be better able to compensate for temperature fluctuations. It may be good in some cases.

In addition, the emitter output of the current detection PNP transistor 14 is connected to a terminal other than the collector of the semiconductor amplification transistor 1 as in this embodiment, especially when the output of the semiconductor integrated circuit is large. 14, the influence of the high frequency signal on the current detection operation can be eliminated.

Also, between the detection current control PNP transistor 14 and the base of the semiconductor amplification transistor 10, a DC amplification N
By providing the PN type transistor 30, according to this embodiment, compared to the first embodiment, the NPN type) landestor 3
Although a voltage as high as the 00 base-emitter voltage is required, the current capacity of the PNP transistor 14 for controlling the detection current can be a reciprocal of the DC amplification factor of the NPN transistor 3o, so it can be small.

Effects of the Invention As described above, the present invention provides current detection type automatic power control that uses the saturation voltage of a transistor as part of the current detection loop, and also uses a plurality of diodes and a constant current circuit for the reference voltage. By providing a circuit and applying the control voltage to the base of a semiconductor amplification transistor, semiconductor amplification can be used particularly against fluctuations in the DC current amplification factor of the transistor, as well as fluctuations in power supply voltage, temperature, or load impedance. The current flowing through the transistor can be kept constant and output fluctuations can be reduced, and the amplifier circuit can be configured with a semiconductor integrated circuit with a grounded emitter, which can increase output power and reduce power consumption. The effect of lower prices is significant.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a semiconductor amplifier circuit according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a semiconductor amplifier circuit according to a second embodiment of the present invention, and FIGS. 3(a) and (b) , (c) is a circuit diagram showing an example of a constant current source circuit which is a main part of the semiconductor amplifier circuit, FIG. 4 is a circuit diagram of a conventional semiconductor amplifier circuit, and FIG.
The figure is a circuit diagram of a conventional automatic power control circuit. DESCRIPTION OF SYMBOLS 1... Semiconductor amplification transistor, 2... Current detection resistor, 3-5... Plural diodes, 6... Constant current source circuit, 7... Diode, 8... Saturation transistor , 11.12... Resistor for voltage division, 14... PN
P-type transistor.

Claims (4)

[Claims] (1) A current detection resistor provided between the collector of a semiconductor amplification transistor and a power supply, and a voltage between the emitter and base of a PNP transistor for detection current control, are used to connect the power supply and a constant current source circuit. A reference potential difference is created by connecting a plurality of forward diodes, a diode voltage, a saturation voltage of a transistor, and a resistor divided voltage are provided in the forward direction between the reference potential differences, and the resistor divided voltage is applied to the detection current control PNP. and a current detection type automatic power control circuit connected to the base of the semiconductor amplification transistor, and further connected to the output control voltage from the collector of the detection current control transistor to the base of the semiconductor amplification transistor. semiconductor amplifier circuit. (2) An inductor is provided between the collector of the semiconductor amplification transistor and the current detection resistor, and the collector of the semiconductor amplification transistor is connected to the emitter of the detected current control PNP transistor. 1. The semiconductor amplifier circuit according to 1. (3) An inductor is provided between the collector of the semiconductor amplification transistor and the current detection resistor, and at the connection point between the current detection resistor and the inductor, a capacitance and the emitter of the detected current control PNP transistor are connected to the ground. 2. The semiconductor amplifier circuit according to claim 1, wherein the semiconductor amplifier circuit is connected. (4) An NPN transistor is provided between the detection current control PNP transistor and the base of the semiconductor amplification transistor, the collector of the NPN transistor is connected to the emitter of the detection current control PNP transistor, and the detection current 2. The semiconductor according to claim 1, wherein the base of the NPN transistor is connected to the collector of the control PNP transistor, and the output from the emitter of the NPN transistor is connected to the base of the semiconductor amplification transistor. Amplification circuit.