JP2006311623A5 - - Google Patents

Description

Variable amplifier and portable radio terminal using the same

  The present invention relates to a variable amplifier whose characteristics as a whole, for example, gain, linearity, noise performance, and the like are variable, and a portable wireless terminal using the variable amplifier as an amplifier for a received signal.

  In portable radio terminals, there are situations in which received power changes greatly or transmission power needs to be adjusted. Therefore, many variable gain amplifiers that vary the gain are used.

  Among them, in the variable gain amplifier in the receiving circuit, when the reception power is small, noise is minimized and high gain is required. When the received power is large, it is important to realize high linearity so as not to be distorted by a high received signal.

  As one form of a variable gain amplifier having such performance, there are variable gain amplifiers described in Non-Patent Document 1 and Non-Patent Document 2. This variable gain amplifier combines a plurality of amplifiers having the same characteristics and a multistage attenuator to realize low noise when the gain is high and high linearity when the gain is kept low.

  As described above, the variable gain amplifier in the receiving circuit of the portable wireless terminal needs to satisfy both a wide variable range, low noise, and high linearity. As a method for realizing this, there is a variable gain amplifier using a differential circuit.

In Patent Document 1, a plurality of variable gain amplifier circuits for attenuating gain according to an increase in control voltage input from the outside are connected in parallel, and each of the variable gain amplifier circuits is connected to the first transistor. The emitter and the emitter of the second transistor are each connected to a constant current source, and the emitter of the first transistor and the emitter of the second transistor are connected to each other via an emitter resistor, and an input signal is applied to the first transistor. An input unit that outputs a collector current from each collector of the first and second transistors; an output unit that receives the collector current output from the input unit and outputs an output signal with a gain corresponding to the control voltage; A variable gain amplifier is disclosed.
JP 2002-252532 A (published September 6, 2002) “A Low-Noise Wideband Variable-Gain Amplifier Using an Interpolated Ladder Attenuator”, ISSCC Digest of Technical Papers, pp.280-281, Feb. 1991 IEICE Technical Report Vol. 96, no. 462, ED96-198, pp. 9-14 (1997)

  However, the variable gain amplifiers described in Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1 operate when a differential signal is input as an input signal. It cannot be directly connected to the signal source of the (unbalanced) signal. That is, when a variable gain amplifier is used for a receiving circuit, a signal output from an antenna that is a signal source of the variable gain amplifier is a single-ended signal. Therefore, when the conventional variable gain amplifier is used in a receiving circuit, it is indispensable to provide a balun for converting a single-ended signal output from an antenna into a differential signal. This balun is difficult to create on an integrated circuit by a silicon process. Therefore, when the conventional variable gain amplifier is used for a receiving circuit, it is difficult to create the entire receiving circuit on an integrated circuit. If a balun is used as a component (chip component) outside the integrated circuit in the receiving circuit, it is difficult to prevent an increase in the mounting area and thickness of the receiving circuit. Further, when a balun is used in the receiving circuit, the received power is reduced due to the loss of the balun, and the receiving sensitivity and the like are degraded.

  The present invention has been made in view of the above-described conventional problems, and its purpose is to connect directly to a single-ended signal source such as an antenna or a filter connected thereto without interposing a balun or the like. It is an object of the present invention to provide a portable wireless terminal that has a variable amplifier and a receiving circuit that have a reduced mounting area and thickness and are excellent in characteristics such as reception sensitivity.

In order to solve the above-described problem, the variable amplifier of the present invention has a plurality of cascaded unit amplification stages in which the emitter of the additional bipolar transistor is connected to the collector of a grounded-emitter bipolar transistor whose base is the signal input end. ,
The signal input terminals of these unit amplifier stages are sequentially connected in series via an attenuator, and the output of the unit amplifier stage is the current flowing through the amplifier connected to a common load and the base of each of the emitter-grounded bipolar transistors. A base current control unit that controls the base voltage of each of the additional bipolar transistors, and the voltage control unit has a current that flows into the base of the common emitter bipolar transistor equal to or less than a predetermined current value. In this case, the base voltage of the additional transistor is brought close to 0V .

In order to solve the above-described problem, the variable amplifier according to the present invention includes a cascaded unit amplifier stage in which the source of the additional field effect transistor is connected to the collector of a grounded-emitter bipolar transistor having the base as a signal input end. There are a plurality of signal input terminals of the unit amplification stages sequentially connected in series via an attenuator, and the output of the unit amplification stage is connected to a common load, and the common emitter bipolar transistor A base current control unit that controls a current flowing through the base; and a gate voltage control unit that controls a gate voltage of each of the additional field effect transistors, wherein the voltage control unit receives a current flowing into the base of the common emitter bipolar transistor. The gate voltage of the additional transistor is brought close to 0V when the current value is equal to or lower than a predetermined current value. .

  In order to solve the above problems, the portable wireless terminal of the present invention includes an amplifier that amplifies a received signal, and the amplifier is a variable amplifier having the above-described configuration.

The variable amplifier of the present invention has a plurality of cascade-connected unit amplification stages in which the emitter of the additional bipolar transistor is connected to the collector of a grounded-emitter bipolar transistor whose base is the signal input end, and the signal input of these unit amplification stages Ends are sequentially connected in series via an attenuator, the output of the unit amplifier stage is an amplifier connected to a common load, and a base current controller for controlling the current flowing through the base of each of the grounded emitter bipolar transistors And a base voltage control unit for controlling the base voltage of each additional bipolar transistor. Each unit amplifier is not a differential circuit but a simple grounded emitter. Therefore, the input is single-ended, and a single-ended / differential converter such as a balun is not required when connecting to a single-ended signal source such as an antenna or a filter connected thereto. Thereby, it is possible to directly connect to a single-ended signal source. Further, if the characteristics of the signal paths are appropriately adjusted and the current flowing through the base of each transistor is appropriately controlled, characteristics such as a variable gain range, linearity, and noise can be satisfied.

The variable amplifier of the present invention has a plurality of cascaded unit amplification stages in which the source of the additional field effect transistor is connected to the collector of a grounded-emitter bipolar transistor having the base as a signal input terminal, and the unit amplification stages. Are connected sequentially in series via an attenuator, and the output of the unit amplifier stage is an amplifier connected to a common load, and a base current for controlling the current flowing through the bases of the common emitter bipolar transistors. The control unit includes a gate voltage control unit that controls the gate voltage of each additional field effect transistor, and each unit amplifier is not a differential circuit but a simple grounded emitter. Therefore, the input is single-ended, and a single-ended / differential converter such as a balun is not required when connecting to a single-ended signal source such as an antenna or a filter connected thereto. Thereby, it is possible to directly connect to a single-ended signal source. Further, if the characteristics of the signal paths are appropriately adjusted and the current flowing through the base of each transistor is appropriately controlled, characteristics such as a variable gain range, linearity, and noise can be satisfied.

In particular, the variable amplifier of the present invention, e Bei additional transistor having an emitter connected or source is connected to the collector of the transistor, the collector or drain of the additional transistor is substantially connected to a load, the actual since the qualitative cascaded, it is possible to suppress the Miller effect can be improved variable range of gain, the linearity of the characteristic.

In the variable amplifier according to the present invention, the additional transistor is a plurality of additional transistors having emitters or sources connected to the collectors of different transistors, so that leakage of a signal from a non-operating grounded transistor is prevented. And high signal separation characteristics can be obtained. As a result, the gain variable range can be expanded and the linearity can be improved.

The variable amplifier of the present invention, since the e Bei voltage control unit for controlling the base voltage or the gate voltage of the plurality of additional transistors, the base voltage or the transistor of the gate voltage common emitter of the plurality of additional transistor It can be actively turned off according to the operating condition. As a result, further improvement in characteristics can be obtained.

In particular, the variable amplifier of the present invention, since the voltage control unit, when the current flowing into the base of the transistor is less than a predetermined current value, in which the base voltage or the gate voltage of the additional transistor to substantially zero It is possible to suppress an increase in transistor distortion when the base current of the grounded-emitter transistor is near zero (off).

  In the variable amplifier according to the present invention, each of the transistors constitutes a unit amplifier. When at least one of the unit amplifiers has a characteristic different from the others, the transistor depends on a characteristic required for each unit amplifier. Thus, the characteristics of each unit amplifier can be optimized, and the characteristics of the entire variable amplifier can be greatly improved.

  In the variable amplifier according to the present invention, the base current control unit may be connected to the base of each transistor so that the total consumption current of the plurality of transistors changes according to a change in a ratio of currents flowing through the bases of the transistors. In the case of controlling the flowing current, the current consumption of each transistor can be adjusted according to the characteristics required for the unit amplifier constituted by each transistor. Therefore, the current consumption of the entire variable amplifier can be reduced.

  In the portable radio terminal of the present invention, an antenna or a band-pass filter directly connected to the antenna can be directly connected to the input of the variable amplifier, which is necessary for a portable radio terminal using a conventional differential variable gain amplifier circuit. The balun that was was eliminated. By eliminating the need for a balun, not only the size of the entire circuit of the portable wireless terminal can be reduced, but also a decrease in received power due to a balun loss can be prevented. Therefore, it is possible to provide a portable wireless terminal that is smaller, has higher performance (high sensitivity), and can operate for a long time.

[ Reference form 1]
One embodiment of the present invention will be described with reference to FIGS. Variable amplifier of the present reference embodiment, by using by switching a plurality of unit amplifiers connected in parallel between the signal input end and signal output end, is configured to vary the gain and linearity of the entire variable amplifier ing. As the number of switching stages (= number of unit amplifiers to be switched), an arbitrary number of stages of 2 or more can be selected, but in the example shown in FIG.

The variable amplifier of the present reference embodiment, by switching the unit amplifier so that the gain and linearity of the entire variable amplifier is changed, a plurality of signal paths leading to the signal output terminal via a plurality of transistors from the signal input terminal, at least One has a different gain and linearity from the other. In the example shown in FIG. 1 (described later), the attenuation of a plurality of signal paths from a signal input end to a plurality of transistors is different from each other.

Further, the variable amplifier of the present reference embodiment, the individual units amplifiers are composed only of transistors of the first stage. The variable amplifier of the present reference embodiment, using the npn type bipolar transistor (bipolar transistor) as a transistor. Further, the variable amplifier of the present reference embodiment, all the plurality of transistors, a transistor having the same characteristics, the emitter area of the concrete using the SiGe bipolar transistor is 20 [mu] m × 0.5 [mu] m.

Figure 1 is a circuit diagram showing a configuration of a variable amplifier in accordance with an embodiment of reference of the present invention (provided that the base current control circuit is shown in block). Variable amplifier of the present reference embodiment, as shown in FIG. 1, three transistors for amplifying a signal, a first transistor Q1, a second transistor Q2 and the third transistor Q3,, the base current control described later A circuit (base current control unit; base current switching circuit) 1.

  Transistors Q1, Q2, and Q3 are arranged in parallel between an input terminal (signal input terminal) Input to which a signal including a DC component is input and an output terminal (signal output terminal) Output for outputting an amplified signal. It is connected. The emitters of the transistors Q1, Q2, and Q3 are grounded. The collectors of the transistors Q1, Q2, and Q3 are connected to the output terminal Output, and are connected to one end of a resistor RL that is a common load resistor. The other end of the resistor RL is supplied with a power supply voltage. Connected to the power line Vcc.

  The input terminal Input is connected to the base of the first transistor Q1 via a capacitor Csr1 that blocks the DC component of the input signal. The input terminal Input is connected to the base of the second transistor Q2 via the capacitor Csr1 and the attenuator AT1 for attenuating the input signal. The attenuator AT1 includes a capacitor Csr2 connected in series with the base of the first transistor Q1 (in series with the capacitor Csr1), and a signal path after the capacitor Csr2, that is, the capacitor Csr2 and the second transistor Q2. The capacitor Csh2 is shunt-connected between the signal path and the ground. Similarly, the input terminal Input is connected to the base of the third transistor Q3 via the capacitor Csr1, the attenuator AT1, and the attenuator AT2 for attenuating the input signal. The attenuator AT2 includes a capacitor Csr3 connected in series with the base of the second transistor Q2 (in series with the capacitor Csr2), and a signal path after the capacitor Csr3, that is, the capacitor Csr3 and the third transistor Q3. The capacitor Csh3 is shunt-connected between the signal path and the ground.

  Here, three signal paths from the input terminal Input to the output terminal Output via the transistors Q1, Q2, and Q3 (hereinafter referred to as “signal path via transistor Q1,” “signal path via transistor Q2,” and “ Consider the characteristics of the "signal path via transistor Q3". Here, it is assumed that the same current flows to the bases of the transistors Q1, Q2, and Q3. First, since the signal input to the input terminal Input is input to the transistor Q1 without passing through the attenuator, the signal path via the transistor Q1 has the highest gain among the three signal paths. On the other hand, since the signal input to the input terminal Input is input to the transistor Q2 via the attenuator AT1, the signal path via the transistor Q2 has a lower gain than the signal path via the transistor Q1. On the other hand, the linearity is higher than that of the signal path via the transistor Q1. Since the signal input to the input terminal Input is input to the transistor Q3 via the attenuators AT1 and AT2, the signal path via the transistor Q3 has a lower gain than the signal path via the transistor Q2. The linearity becomes higher than the signal path via the transistor Q2.

  Further, terminals Ib1, Ib2, and Ib3 of the base current control circuit 1 are connected to the bases of the transistors Q1, Q2, and Q3, respectively, and the current (base current) that flows into the bases of the transistors Q1, Q2, and Q3 is the base current. It is controlled independently by the control circuit 1.

  As shown in FIG. 2, the base current control circuit 1 includes resistors Rc1, Rc2, and Rc3 for generating reference voltages, a resistor Rref for setting a total base current, and a field effect that forms a current mirror circuit for setting the total current. Transistors Qref and Qbcs, field effect transistors Qb1 and Qb2 constituting a first differential pair, and field effect transistors Qb3 and Qb4 constituting a second differential pair. The transistors Qref, Qbcs, Qb1, Qb2, Qb3, and Qb4 are p-channel MOS (Metal Oxide Semiconductor) transistors.

  The transistors Qbref and Qbcs form a current mirror circuit by connecting the gate and source of the transistor Qbref and the gate of the transistor Qbcs. The transistor Qbref has a drain connected to the power supply line Vcc, a source and a gate connected to one end of the resistor Rref, and the other end of the resistor Rref grounded. The transistor Qbcs has a drain connected to the power supply line Vcc and a source connected to the drains of the transistors Qb1 and Qb2. This current mirror circuit sets a total current (hereinafter referred to as “total base current”) that should flow through the bases of the transistors Q1, Q2, and Q3, and supplies a current equal to the set total current to the drains of the transistors Qb1 and Qb2. It is supposed to flow. The current flowing through the gate and source of the transistor Qbref is determined by the current setting resistor Rref, and the current (total base current) flowing into the drains of the transistors Qb1 and Qb2 is determined from the determined current by the current mirror circuit. If the transistors Qbref and Qbcs constituting the current mirror circuit have the same size, the current (total base current) flowing into the drains of the transistors Qb1 and Qb2 is the same as the current determined by the current setting resistor Rref. It becomes a constant current.

  The resistors Rc1, Rc2, and Rc3 are connected in series between the power supply line Vcc to which the power supply voltage is applied and the ground, and divide the power supply voltage to obtain the reference voltages Vr1 and Vr2 (the magnitude of the reference voltage Vr1 <the reference voltage Vr2). Is generated).

  The drains of the transistors Qb1 and Qb2 are connected to each other to form a first differential pair. A reference voltage Vr2 is applied to the gate of the transistor Qb1, while a variable control voltage Vctrl is applied to the gate of the transistor Qb2 from the outside via the control voltage terminal Vctrl. The source of the transistor Qb1 is connected to the base of the transistor Q1 via the terminal Ib1, and the source of the transistor Qb2 is connected to the drains of the transistors Qb3 and Qb4. The first differential pair determines the ratio of the current flowing through the base of the transistor Q1 and the current flowing through the drains of the transistors Qb3 and Qb4 according to the magnitude relationship between the control voltage Vctrl and the reference voltage Vr2.

  The drains of the transistors Qb3 and Qb4 are connected to each other to form a second differential pair. The reference voltage Vr1 is applied to the gate of the transistor Qb3, while the variable control voltage Vctrl is applied to the gate of the transistor Qb4 from the outside via the control voltage terminal Vctrl. The source of the transistor Qb3 is connected to the base of the transistor Q2 via the terminal Ib2, the source of the transistor Qb4 is connected to the base of the transistor Q3 via the terminal Ib3, and the drains of the transistors Qb3 and Qb4 It is connected to the. This second differential pair determines the ratio of the current flowing through the base of the transistor Q2 and the current flowing through the base of the transistor Q3 according to the magnitude relationship between the control voltage Vctrl and the reference voltage Vr1.

  As a result, in the base current control circuit 1, the total base current sent to the drains of the transistors Qb1 and Qb2 determined by the transistors Qbref and Qbcs is output by the transistors Qb1, Qb2, Qb3, and Qb4 according to the control voltage Vctrl. It is distributed to Ib1, Ib2, and Ib3. As a result, the ratio of the values Ib1, Ib2, and Ib3 of the currents flowing through the terminals Ib1, Ib2, and Ib3 (currents flowing through the bases of the transistors Q1, Q2, and Q3) depends on the control voltage Vctrl as shown in FIG. Change in an analog fashion. FIG. 3 shows switching characteristics (changes in base current with respect to control voltage) of currents (base currents) applied to the bases of the transistors Q1, Q2, and Q3.

  In this case, the ratio of the current value Ib1 to the total base current is 0% when the control voltage Vctrl is less than about 0.9V, and is 0 while the control voltage Vctrl rises from about 0.9V to about 2.35V. % Continuously increases from 100% to 100% when the control voltage Vctrl exceeds about 2.35V. The ratio of the current value Ib2 to the total base current is 0% when the control voltage Vctrl is less than about 0.2V, and from 0% to about 1% while the control voltage Vctrl rises from about 0.2V to about 1.35V. While increasing continuously to 80%, while the control voltage Vctrl increases from about 1.35V to about 2.35V, it continuously decreases from about 80% to 0%, and the control voltage Vctrl exceeds about 2.35V. And 0%. The ratio of the current value Ib1 to the total base current is 100% when the control voltage Vctrl is less than about 0.2V, and from 100% to 0 while the control voltage Vctrl rises from about 0.2V to about 1.45V. When the control voltage Vctrl exceeds about 1.45V, it becomes 0%. In this case, while the control voltage Vctrl rises from about 1.35V to about 2.35V, it continuously decreases from about 80% to 0%, and when the control voltage Vctrl exceeds about 2.35V, it becomes 0%. In this case, when the control voltage Vctrl is in the range of about 0.2V to about 2.35V, the ratio of the current values Ib1, Ib2, and Ib3 flowing through the bases of the transistors Q1, Q2, and Q3 depends on the control voltage Vctrl. Change continuously.

  Next, the operation of the variable amplifier when the control voltage Vctrl is changed will be described. When the control voltage Vctrl is sufficiently high (about 2.4 V or more) with respect to the reference voltages Vr1 (= 0.85 V) and Vr2 (= 1.7 V), the transistors Qb2 and Qb4 of the base current control circuit 1 Since it is in the OFF state, all of the total base current set by the current mirror circuit for setting the total current (transistors Qref and Qbcs) is supplied to the base of the transistor Q1 of the amplifier via the transistor Qb1. Accordingly, the other transistors Q2 and Q3 are turned off. In this state, since the signal input to the input terminal Input is input to the transistor Q1 without passing through the attenuator, the gain becomes the highest. In this state, the linearity of the transistor Q1 itself appears as it is in the IIP3 (Input 3rd order Intercept Point) that is an index of linearity of the entire variable amplifier.

  As the control voltage Vctrl decreases, a part of the current supplied to the base of the transistor Q1 is supplied to the base of the transistor Q2. That is, as the control voltage Vctrl decreases, the base current of the transistor Q1 gradually decreases, while the base current of the transistor Q2 gradually increases. As a result, the collector current of the transistor Q1 decreases, and the gain gradually decreases. On the other hand, the transistor Q2 increases in collector current and gradually gains. Since the signal path via the transistor Q2 has a lower gain when the base current is the same as the signal path via the transistor Q1 as described above, the gain of the entire variable amplifier decreases (see FIG. 4). Further, as described above, the linearity of the entire variable amplifier increases because the signal path via the transistor Q2 has higher linearity when the same base current is used than the signal path via the transistor Q1 (see FIG. 4). ).

  Eventually, when the control voltage Vctrl decreases, the gain of the transistor Q2 increases as the collector current of the transistor Q2 increases, and the transistor Q1 is almost turned off. In this case, since the attenuator AT1 is included in the input of the transistor Q2, the gain of the entire variable amplifier is reduced. However, the IIP3 of the entire variable amplifier has an attenuation factor expressed in decibels (dB) in the characteristics of the transistor Q2. It will be added.

  When control voltage Vctrl further decreases (when it is about 0.2 V or less), transistors Qb1 and Qb3 are turned off. Therefore, all of the total base current set by the resistor Rref and the transistors Qbref and Qbcs of the base current control circuit 1 is supplied to the base of the transistor Q3 via the transistor Qb4, and all the other transistors Q1 and Q2 are turned off. It becomes. In this state, since the signal input to the input terminal Input is input to the transistor Q3 via the attenuators AT1 and AT2, the gain of the entire variable amplifier is the lowest, and conversely, the IIP3 of the entire variable amplifier is the highest. Get higher.

  FIG. 4 shows the gain and IIP3 characteristics with respect to the control voltage Vctrl.

Thus, the variable amplifier of the present reference embodiment, can gain variable over a wide range, and, in the state of low gain large signal is input, it is possible to achieve high linearity. Variable amplifier of the present reference embodiment, the format of the amplifier circuit is not a differential circuit which is often used in silicon RFIC (Radio Frequency Integrated Circuit), and has a grounded emitter circuit. Therefore, the input signal in the variable amplifier of the present reference embodiment has a single-ended input (unbalanced input), not a differential input. Therefore, the variable amplifier of the present reference embodiment can be directly connected to a single-ended signal source such as an antenna or a filter.

Further, in the variable amplifier of the present reference embodiment, in essence, because the portion consumes power only load resistor an amplifier of the first stage transistor can be operated at a low power supply voltage, for example, it operates from about 1V Can be made. On the other hand, in the differential circuit, a current source, an amplifying unit, and a load resistor are necessary, and the amplifying unit needs to be stacked in two stages, so that the power supply voltage cannot be lowered so much.

  In the variable amplifier shown in FIG. 1, the gain characteristic (FIG. 4) with respect to the control voltage has a slight undulation and the linearity is not so high. However, the gain characteristic with respect to the control voltage can be approximated to a straight line by increasing the number of switching stages (number of unit amplifiers to be switched). On the other hand, increasing the number of switching stages increases the circuit scale. Therefore, the number of switching stages is preferably determined by a balance between the circuit scale and the linearity of the gain characteristic with respect to the control voltage.

Further, in this preferred embodiment has used the npn type transistor, it is possible to configure a similar variable amplifier in a pnp transistor.

Furthermore, those in this reference embodiment, as an attenuator interposed between the input terminal Input and the transistor Q2 · Q3, was used attenuators AT1 · AT2 of the capacitor, the configuration of the attenuator of the capacitor is limited particularly is not. Further, as shown in FIG. 5, a resistor attenuator AT3 and attenuator AT4 may be used in place of the capacitor attenuator AT1 and attenuator AT2. However, in the case of using the attenuator AT3 and the attenuator AT4 by resistors, a capacitor is provided between each of the emitter-grounded transistor Q1, transistor Q2, and transistor Q3 and the attenuators AT3 and AT4 in order to enable operation. It is necessary to separate the bases of the transistors Q1, Q2, and Q3 and the attenuators AT3 and AT4 by inserting Cdc1, the capacitor Cdc2, and the capacitor Cdc3, respectively. In the variable amplifier shown in FIG. 5, a resistor Rsr1 is provided between the bases of the transistors Q1, Q2, and Q3 and the input terminal Input.

  The attenuator AT3 includes a resistor Rsr2 connected in series with the base of the first transistor Q1 (in series with the resistor Rsr1), and a signal path after the resistor Rsr2, that is, the resistor Rsr2 and the first resistor The resistor Rsh2 is connected to the signal path connecting the base of the second transistor Q2 with a shunt between the signal path and the ground. The attenuator AT4 includes a resistor Rsr3 connected in series with the base of the second transistor Q2 (in series with the resistor Rsr2), and a signal path after the resistor Rsr3, that is, the resistor Rsr3 and the second resistor The resistor Rsh3 is connected to the signal path connecting the base of the third transistor Q3 with a shunt between the signal path and the ground.

  Using the resistance type attenuators AT3 and AT4, (1) the size of the variable amplifier, especially the chip area when realized by an integrated circuit chip, is reduced. (2) Signal leakage in the variable amplifier, especially the component circuit. There are advantages such that signal leakage through the substrate is reduced when (2) is mounted on one substrate, and (3) matching is easy. The configuration of the attenuator using the resistor is not particularly limited. In the configuration shown in FIG. 5, the resistor Rsr1 is not always necessary.

Further, in this reference embodiment, as the base current control circuit, using an analog circuit configuration shown in FIG. However, the base current control circuit for this base current controls the ratio of the current values Ib1, Ib2, and Ib3 flowing through the bases of the transistors Q1, Q2, and Q3 to the control voltage Vctrl within a predetermined numerical range. There is no particular limitation as long as it can be continuously changed according to Vctrl. For example, the base current control circuit may be configured to digitally control the base currents of the transistors Q1, Q2, and Q3 using a D / A (digital-analog) converter or the like. Even when the base currents of the transistors Q1, Q2, and Q3 are controlled by an analog circuit, a base current control circuit of another circuit type can be used.

Furthermore, the base current control circuit of this preferred embodiment, the total base current is almost constant so as design. However, the total base current is not necessarily constant. It is also possible to pass a large amount of current through the amplifying unit where linearity is important and reduce the current flowing through the amplifying unit where linearity is not so important. That is, among the base currents of the transistors Q1, Q2, and Q3, the total base current when the base current of the transistor Q3, which is important for linearity, is the largest is made larger than the total base current when the base current of the transistor Q2 is the largest. Alternatively, the total base current when the base current of the transistor Q1 whose linearity is not so important is the largest can be made smaller than the total base current when the base current of the transistor Q2 is the largest. Alternatively, negative feedback can be applied to the transistors Q2 and Q3 so that sufficient linearity can be obtained, and the base current can be reduced. The transistor Q1 needs to satisfy all the characteristics of high linearity, low noise, and high gain, so that a certain amount of current is necessary. However, the transistors Q2 and Q3 have a gain and noise characteristics of Since there is some margin, current consumption can be reduced by using negative feedback. However, if the total base current of the transistors Q1, Q2, and Q3 is constant, there is an advantage that the output DC voltage is substantially constant.

Further, the variable amplifier of the present reference embodiment, a plurality of signal paths leading to the signal output terminal via a plurality of transistors from the signal input terminal had all different characteristics. However, there may be a plurality of signal paths having the same characteristics as long as at least one of these signal paths has a different characteristic from the others.

Also, some characteristics by the variable amplifier of the present reference embodiment, the gain and linearity were so changed by controlling the current flowing to the base of each transistor, for controlling the current flowing to the base of each transistor It is only necessary for the to change.

As described above, the variable amplifier of the present reference embodiment is composed of a plurality of bipolar transistors, the emitter of the transistor is substantially grounded, the collector of the transistor in the amplifier that is connected to the substantially same load In this configuration, the characteristics of the entire amplifier are varied by changing the base current of each transistor. With this configuration, since it is not a differential circuit but a simple grounded emitter, the input is single-ended, and a single-ended / differential converter such as a balun is not required. In addition, characteristics such as variable gain range, linearity, and noise performance can be satisfied.

Further, as described above, the variable amplifier of the present reference embodiment, in the amplifier circuit of the plurality of grounded emitter, a base current of the bipolar transistors used in their amplification continuously by an analog signal (an analog manner) By changing the characteristics of the entire variable amplifier by switching, a wide variable gain range and linearity are realized.

  Although there are a large number of single-ended variable gain amplifiers at present, in many cases, the gain only changes, and the linearity does not change or the linearity deteriorates as the gain decreases. On the other hand, the single-ended variable gain amplifier according to the present invention has a feature that the linearity improves as the gain decreases, as described above. As for the variable gain amplifier having such a feature, the preceding example is seen in the differential input type as described in the section of the prior art, but the preceding example is not seen in the single-ended type. As described above, the variable gain amplifier according to the present invention is characterized in that it is single-ended in a variable amplifier that has low noise at high gain and high linearity at low gain.

[ Reference form 2]
If described with reference to FIG. 6 with the other references in the form of the present invention is as follows. For convenience of explanation, members having the same functions as those shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

Since the variable amplifier of the reference form 1 uses a simple grounded emitter, the capacitance between the base / collector of the transistors Q1, Q2, and Q3 is increased by the Miller effect. For this reason, the variable amplifier of the reference form 1 does not have very good high frequency characteristics.

Therefore, in the variable amplifier of the present reference embodiment, using a cascade connection to improve the high frequency characteristics. The configuration of the variable amplifier according to this reference embodiment will be described below .

In the reference embodiment 1 of the variable amplifier, the collector of the transistor Q1 · Q2 · Q3 emitter grounded, while was connected to a load resistor RL, the variable amplifier of the present reference embodiment, the common emitter Transistors (additional transistors) Q4 are connected in cascade to the transistors (bipolar transistors) Q1, Q2, and Q3, and the emitters of the transistors Q4 are connected to the collectors of the transistors Q1, Q2, and Q3 having common emitters. The collector is connected to a resistor RL that is a load. The transistor Q4 is grounded at a high frequency when a fixed bias voltage Vbb (= 2.0 V) is applied to its base via a terminal Vbb. Hereinafter, a transistor grounded in this way at high frequency is referred to as a “base-grounded transistor”. Variable amplifier of the present reference embodiment, except this difference has a configuration similar to the variable amplifier of the reference embodiment 1.

The variable amplifier of the present reference embodiment, as in the first reference, with an npn bipolar transistor as a transistor Q1 · Q2 · Q3 emitter grounded. An npn bipolar transistor was also used as the base-grounded transistor Q4. The base current of the common emitter of the transistor Q1 · Q2 · Q3 is, as in the first reference, and controlled by the base current control circuit 1 shown in the circuit diagram of FIG. The variable amplifier of the present reference embodiment, it is possible to obtain the same effect as in the first reference.

For the variable amplifier of the variable amplifier and the present reference embodiment of Reference Embodiment 1 shows the result of simulating the frequency characteristic of the gain in Fig. The variable amplifier of the present reference embodiment, as compared with the variable amplifier of Reference Embodiment 1, the absolute value of the gain is increased, and the frequency characteristic is also slightly improved. This is considered to be a result of the mirror effect being suppressed by the cascade connection.

In the variable amplifier according to the present embodiment, a bipolar transistor Q4 with a common base is used as a transistor (additional transistor) connected in cascade to the collectors of the common emitter transistors Q1, Q2, and Q3. A field effect transistor (FET) such as a MOS transistor may be used. In this case, the source of the field effect transistor is connected to the collectors of the transistors Q1, Q2, and Q3, and the drain of the field effect transistor is connected to the resistor RL that is a load.

As described above, the variable amplifier of the present reference embodiment includes a transistor of a first group and a second transistor, the emitter of the bipolar transistor of the first group are sequentially grounded, the first group The collector of the second transistor is substantially connected to the emitter or source of the second transistor, and the base or gate of the second transistor is grounded at a high frequency to form a grounded base circuit or a gate grounded circuit. The collector or drain of the transistor is configured to vary the characteristics of the entire amplifier by adjusting the base current of each of the first group of transistors in the amplifier substantially connected to the load. In this circuit form, to become substantially cascaded, it is possible to suppress the Miller effect, the variable range of more gain than the reference mode 1, it is possible to improve the linearity characteristics.

[ Reference form 3]
If described with reference to FIG. 7 for the other reference embodiment of the present invention is as follows. For convenience of explanation, members having the same functions as those shown in the reference embodiment 1 or 2 are denoted by the same reference numerals, and description thereof is omitted.

For the variable amplifier of the present reference embodiment will be described below. In the variable amplifier according to the second embodiment, a common transistor Q4 is used for all of the grounded emitter transistors Q1 to Q3 as a grounded base transistor connected in cascade to a grounded emitter transistor. In contrast, in the variable amplifier of the present reference embodiment, the transistor Q1 emitter grounded, Q2, and transistor individually common base for each Q3 Q41, Q42, and Q43 connected in cascade, which transistors Q41, Q42, And the emitters of Q43 are connected to the collectors of transistors Q1, Q2, and Q3 having common emitters, and the collectors of the transistors Q41, Q42, and Q43 are connected to a resistor RL that is a common load resistance. Variable amplifier of the present reference embodiment, except this difference has a configuration similar to the variable amplifier of the reference to the second embodiment. In the variable amplifier of this reference embodiment, npn bipolar transistors are used for all the transistors as in Reference Embodiments 1 and 2. The collector of the transistor Q4 is connected to a resistor RL which is a load. Transistors Q41, Q42, and Q43 have fixed bias voltages Vbb1, Vbb2, and Vbb3 (= 2.0V) applied to their bases via terminals Vbb1, Vbb2, and Vbb3, and in terms of high frequency Grounded.

In the variable amplifier of the reference form 2, even when the grounded emitter transistors Q1 to Q3 are turned off, the signal leaks through the capacitance component between the base / collector of the grounded emitter transistors Q1 to Q3. In contrast, in the variable amplifier of the present reference embodiment, the fact that the transistor Q1 emitter grounded, Q2, and individually grounded base relative to Q3 transistors Q41, Q42, and Q43 is provided, the transistors of the grounded emitter Q1~Q3 At the same time, the collector currents of the grounded transistors Q41 to Q43 do not flow, and the grounded transistors Q41 to Q43 are also turned off. Accordingly, since the signal leakage path of the grounded transistors Q41 to Q43 is only a capacitance component between the collector and the emitter that is considerably smaller than the capacitance component between the base and the collector, high signal separation characteristics (isolation characteristics) can be obtained. .

A common base of the transistor transistor Q1~Q3 in common with the reference according to a second variable amplifier ( "common base shared"), the variable of this preferred embodiment of the transistor of the grounded-base was isolated corresponding to each transistor Q1~Q3 FIG. 7 shows a simulation result of the gain characteristic with respect to the control voltage and the IIP3 characteristic with respect to the control voltage for the amplifier (“base ground isolation”). Variable amplifier of the present reference embodiment, compared with the transistor of the common base reference according to the second variable amplifier in common, with the isolation characteristic at low gain is improved, it can be seen that the IIP3 characteristic is greatly improved .

It should be noted that in the present reference embodiment, was to add a transistor Q41~Q43 of each base ground to transistor Q1~Q3 of all of the emitter ground. However, the grounded-base transistors are not necessarily individually attached to all the grounded-emitter transistors Q1 to Q3, and one grounded-base transistor may be attached to a plurality of grouped grounded transistors. For example, in the variable amplifier of the present embodiment , it is possible to attach one base-grounded transistor to the transistors Q2 and Q3.

Further, in the variable amplifier of the present reference embodiment, in the same manner as in Reference Embodiment 2, as the transistor (additional transistor) for cascade connection to the collector of the transistor Q1 · Q2 · Q3 emitter grounded, the bipolar base transistor Q41・ Instead of Q42 and Q43, use a field effect transistor such as a MOS transistor whose gate is grounded, connect the source of the field effect transistor to the collector of the transistors Q1, Q2 and Q3, and load the drain of the field effect transistor May be connected to the resistor RL.

As described above, the variable amplifier of the present reference embodiment, the first group of transistors and a second reference embodiment 2 of the variable amplifier comprising a transistor, a configuration wherein the second transistor is a plurality. In other words, the variable amplifier of the present reference embodiment, with respect to the variable amplifier of Reference Embodiment 2, a configuration obtained by dividing the transistors of the grounded base or gate grounded cascaded circuit to multiple. As a result, signal leakage from the non-operating grounded-emitter transistor can be prevented, and high isolation characteristics can be obtained. As a result, the gain variable range can be expanded and the linearity can be improved.

[Embodiment 1]
About implementation of the present invention with reference to FIG. 8, and 9, it is as follows. For convenience of explanation, the members having the same functions as the members shown in either of Reference Embodiment 1 to 3, the same reference numerals, and description thereof is omitted.

In the variable amplifiers of the reference embodiments 2 and 3 so far, the bias of the transistors Q1 and Q2 having common emitters is controlled, but the transistors having common bases (Q4 and Q41, Q42, and Q43) have a fixed bias. . In the variable amplifier having such a configuration, the base-grounded transistors (Q4 and Q41, Q42, and Q43) are only passively turned off when the current does not flow. Happens to be turned on. For this reason, the variable amplifiers of the reference embodiments 2 and 3 so far may have insufficient isolation characteristics in order to obtain a wider variable gain range. In addition, since the base-grounded transistors (Q4 and Q41, Q42, and Q43) operate slightly even in the off state, distortion components are also generated, and the linearity may be deteriorated.

Therefore, the variable amplifier of the present embodiment, when the transistor Q1 · Q2 · Q3 of emitter grounding is off, forcibly near 0V the base voltage of the transistor Q41 · Q42 · Q43 grounded base corresponding thereto The base voltages of the base-grounded transistors Q41, Q42, and Q43 are controlled so as to approach each other. As a result, the base-grounded transistors Q41, Q42, and Q43 can be actively turned off to further improve the isolation characteristics.

Variable amplifier of the present embodiment, with respect to the variable amplifier of the terminal Vbb1 · Vbb2 · Vbb3 that vertical connection connects the base voltage control for controlling the base voltage Vbb1 · Vbb2 · Vbb3 transistors of the grounded base Q41 · Q42 · Q43 A circuit is connected.

FIG. 8 shows the configuration of a base voltage control circuit (voltage control unit) connected to the variable amplifier according to the present embodiment .

As shown in FIG. 8 , the base voltage control circuit 2 is different from the base current control circuit 1 shown in FIG. 2 in that a mirror circuit composed of a transistor Qb1c and a transistor Qb1m is provided between the transistor Qb1 and the terminal Ib1. A mirror circuit composed of the transistor Qb2c and the transistor Qb2m is inserted between the Qb3 and the terminal Ib2, and a mirror circuit composed of the transistor Qb3c and the transistor Qb3m is inserted between the transistor Qb4 and the terminal Ib3, respectively. In order to convert the current from the mirror circuit into a voltage, a pair of resistors R1u and R1l and a pair of resistors R2u and R2l are connected between the mirror circuit and the terminals Ib1, Ib2, and Ib3, respectively. , And a set of resistors R3u and R3l. These transistors Qb1c, Qb1m, Qb2c, Qb2m, Qb3c, and Qb3m are all p-type field effect transistors (p-channel MOS transistors).

  In the base voltage control circuit 2, the currents Ib1, Ib2, and Ib3 flow in a direction in which current flows out by a mirror circuit that includes transistors Qbxc (x is 1, 2, 3) and transistors Qbxm (x is 1, 2, 3). Is converted to This current is converted into a voltage by a resistor composed of a resistor Rux (x is 1, 2, 3) and a resistor Rlx (x is 1, 2, 3) and applied to the transistors Q41, Q42, and Q43. Base voltages Vbb1, Vbb2, and Vbb3 to be generated are generated.

  As described above, the base voltage control circuit 2 generates the base currents Ib1, Ib2, and Ib3 according to the control voltage Vctrl, and generates the base voltage based on the base currents Ib1, Ib2, and Ib3.

The currents Ib1, Ib2, and Ib3 flowing into the transistors Qb4, Qb3, and Qb1 shown in FIG. 8 exhibit the control voltage dependency shown in FIG. 3, as in the base current control circuit 1 shown in FIG.

If the gate width of the transistor pair (transistor Qbxc (x is 1, 2, 3) and transistor Qbxm (x is 1, 2, 3)) constituting the mirror circuit is the same,
(Rux + Rlx) × Iref >> the resistance of the resistor R1u · R1l · R2u · R2l · R3u · R3l to satisfy the relationship of the power supply voltage and, when determining the value of the current Iref flowing through the resistor, shown in Figure 9 Such control voltage dependence of the base voltage can be obtained. In FIG. 9 , the same line type (solid line, dotted line, and alternate long and short dash line) indicates the base current of the grounded emitter transistors (Q1 to Q3) or the grounded base transistors (Q41 to Q43) constituting a pair of cascaded transistors. The base voltage is shown. The base voltages Vbb1, Vbb2, and Vbb3 of the grounded transistors Q41 to Q43 are preferably not changed as much as possible during the operation of the grounded emitter transistors (Q1 to Q3). It is desirable that the flowing current is sufficiently larger than the necessary base current.

  Looking at the switching characteristics, when the base voltages Vbb1, Vbb2, and Vbb3 of the base-grounded transistors Q41 to Q43 and the base currents Ib1, Ib2, and Ib3 of the grounded transistors Q1 to Q3 are decreased, the base-grounded transistors Q41 to Q41 are reduced. The base voltages Vbb1 to Vbb3 of Q43 are in the off state (near 0V) after the base currents Ib1 to Ib3 of the transistors Q1 to Q3 having common emitters are sufficiently small. Since the base voltages Vbb1 to Vbb3 of the grounded base transistors Q41 to Q43 are controlled in the vicinity of 0V in a state where the grounded emitter transistors Q1 to Q3 are not operating, higher isolation characteristics can be obtained, and gain suppression and IIP3 The characteristics can be improved.

The circuit for controlling the base voltage of the transistor Q41 · 42 · 43 of the base-grounded, as in the base current control circuit, is not limited to the analog circuit shown in FIG. 8 (base voltage control circuit 2), the other A digital analog control circuit or computer-controlled control signal is generated, and a base voltage of the base-grounded transistors Q41, 42, and 43 is generated from the control signal using a D / A converter. Various configurations such as a circuit for performing control are conceivable.

As described above, the variable amplifier according to the present embodiment is the same as the variable amplifier according to Reference Example 3, except that the base current of the first group of transistors is changed and the base voltages of the plurality of second transistors are changed. Alternatively, the gate voltage is changed. Further, the variable amplifier according to the present embodiment is configured to actively turn off the plurality of grounded base or gate grounded transistors in accordance with the operation status of the grounded emitter transistor. Thereby, further improvement of characteristics can be obtained.

[Embodiment 2 ]
If described with reference to FIGS. 10 and 11, another embodiment of the present invention is as follows. For convenience of explanation, the members having the same functions as the members shown in either reference embodiment 1 to 3 and embodiment 1, the same reference numerals, and description thereof is omitted.

When the characteristics of the variable amplifier of the first embodiment are examined in detail, it can be seen that the IIP3 characteristics deteriorate as the base currents Ib1 to Ib3 of the transistors Q1 to Q3 having common emitters become smaller. In order to improve this characteristic, the variable amplifier according to the present embodiment reduces the base voltages Vbb1 to Vbb3 of the grounded transistors Q41 to Q43 and the base currents Ib1 to Ib3 of the grounded transistors Q1 to Q3. The base currents Ib1 to Ib3 of the grounded emitter transistors Q1 to Q3 are reduced, and the grounded base transistor is forcibly turned off before distortion occurs. Thereby, characteristics can be improved.

Such switching characteristics include resistance values of resistors Rc1, Rc2, and Rc3 that generate reference voltages in the base voltage control circuit 2 shown in FIG. 8 , and resistors R1u, R1l, R2u, and R2l that perform current / voltage conversion. It can be obtained by adjusting the resistance values of R3u and R3l.

Shows the switching characteristics of the base current Ib1~Ib3 transistor Q1~Q3 emitter grounded by the control voltage Vctrl, the switching characteristics of the base voltage Vbb1~Vbb3 transistor Q41~Q43 common base by the control voltage Vctrl in conjunction with FIG. 10 .

In FIG. 9 , the base voltages Vbb1 to Vbb3 of the grounded transistors Q41 to Q43 always have a constant value with respect to the control voltage Vctrl in which the base currents Ib1 to Ib3 of the grounded transistors Q1 to Q3 flow. When the base voltages Vbb1 to Vbb3 of the grounded transistors Q41 to Q43 and the base currents Ib1 to Ib3 of the grounded transistors Q1 to Q3 are decreased, the base currents Ib1 to Ib3 of the grounded transistors Q1 to Q3 are It can be seen that the base voltages Vbb1 to Vbb3 of the grounded base transistors Q41 to Q43 are in the vicinity of 0V since they are completely turned off (near 0V).

On the other hand, in FIG. 10 , when the base currents Ib1 to Ib of the common emitter transistors Q1 to Q3 become about 10% (predetermined value) or less of the predetermined current, the base voltages Vbb1 to Vbb3 of the common base transistors Q41 to Q43 are obtained. Is in the vicinity of 0 V, and it can be seen that it is in an off state (blocking state).

Comparison between the gain characteristic and IIP3 characteristic of the variable amplifier according to the present embodiment ("gain control only at grounded emitter") and the gain characteristic and IIP3 characteristic of the variable amplifier according to the first embodiment ("distortion removal by grounded base") It is shown in Figure 11. It can be seen that in the variable amplifier according to the present embodiment, the deterioration of IIP3 at the control voltage Vctrl in the vicinity of which the transistors Q1 to Q3 are switched is greatly suppressed.

As described above, the variable amplifier of the present embodiment, in the variable amplifier according to the first embodiment, the transistor base current of the emitter-grounded, and a control method of the base voltage or the gate voltage of the transistor of the common base or common gate, In this configuration, the base voltage or gate voltage of the base-grounded or gate-grounded transistor is cut off earlier than the base current of the common-emitter transistor is cut off. In addition, this makes it possible to suppress an increase in distortion in the vicinity of the off-grounded transistor.

[Embodiment 3 ]
If described with reference to FIG. 12, another embodiment of the present invention is as follows. For convenience of explanation, the members having the same functions as the members shown in either reference embodiment 1 to 3 and Embodiment 1-2, the same reference numerals, and description thereof is omitted .

In Reference Embodiments 1 to 3 and Embodiments 1 and 2 so far, the plurality of unit amplifiers (transistors Q1 to Q3) all have the same characteristics (gain and linearity), but the characteristics of the respective unit amplifiers are different from each other. Can be made. When high gain is required, low noise is usually required, but not much linearity is required. However, in a situation where a high signal is input and the gain of the amplifier is set low, high linearity is required.

  As a method of satisfying such characteristics, a negative feedback is not applied to the amplifier closest to the input, and a resistor or an inductor is inserted in the emitter of the transistors Q2 and Q3 in the amplifier after the attenuator. Negative feedback can be applied to Q2 and Q3 to improve linearity.

As shown in FIG. 12 , the variable amplifier according to the present embodiment is different from the variable amplifier of Reference Embodiment 1 shown in FIG. 1 between the emitter of transistor Q2 and the ground and between the emitter of transistor Q3 and the ground. In each case, a resistor Re2 and a resistor Re3 for applying negative feedback are inserted. In this case, one unit amplifier is constituted by the transistor Q2 and the resistor Re2, and one unit amplifier is constituted by the transistor Q3 and the resistor Re3.

  As another method for applying negative feedback to the transistors Q2 and Q3, negative feedback can be applied using a capacitor or a resistor between the base / collector of the transistors Q2 and Q3. However, the noise characteristic is best when an inductor is inserted into the emitter, and is slightly worse when a resistor is inserted into the emitter. When a resistor or capacitor is inserted between the base / collector of the transistors Q2 and Q3 and negative feedback is applied, the noise characteristics are considerably deteriorated.

  Further, as a method for further improving the linearity, it is effective to increase the current density of the transistors Q2 and Q3. The transistor Q1 closest to the input requires a low base resistance in order to realize low noise. Therefore, a relatively large size must be used for the transistor Q1. In order to make the consumption current as small as possible, the current density of the transistor Q1 cannot be increased so much. However, since the specifications for the noise characteristics of the transistors Q2 and Q3 connected after the attenuators AT1 and AT2 are relaxed, the size of the transistors Q2 and Q3 is reduced and the current density of the transistors Q2 and Q3 is increased. , Linearity can be improved.

  By optimizing the characteristics of each unit amplifier by such a method, it is possible to realize low linearity at high gain and high linearity at low gain.

As described above, the variable amplifier according to the present embodiment is characterized in that, in the variable amplifier according to any one of Reference Embodiments 1 to 3 and Embodiments 1 and 2 , the plurality of unit amplifiers configured by the plurality of transistors have characteristics. The configuration includes a plurality of different types of unit amplifiers. In this configuration, the characteristics of the amplifier as a whole can be greatly improved by optimizing the characteristics of the amplifier according to the respective characteristics.

[Embodiment 4 ]
If described with reference to FIG. 13, another embodiment of the present invention is as follows. For convenience of explanation, members having the same functions as those shown in any one of the first to third embodiments and the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted. .

In the variable amplifiers according to the first to third embodiments and the first to third embodiments, the characteristics required for the unit amplifier (transistor Q1) closest to the input are high gain and low noise performance as described above. In order to realize low noise, it is indispensable to lower the base resistance of the transistor Q1, and for that purpose, the size of the transistor Q1 is increased. Further, in order to realize a high gain, a certain amount of current must flow through the transistor Q1. Further, in order to achieve a certain degree of linearity, it is essential to pass a certain amount of current through the transistor Q1. Therefore, the current consumption of the first unit amplifier (transistor Q1) is a large value.

On the other hand, in the variable amplifiers according to the first to third embodiments and the first to third embodiments, the two unit amplifiers configured by the transistors Q2 and Q3 to which signals are input via the attenuators AT1 and AT2 are linear. Is an important characteristic. In order to improve the linearity of these unit amplifiers, there is a method of flowing a large amount of current through the transistors Q2 and Q3. However, the circuit form of the reference embodiment 1 to 3 and Embodiment 1 to 3 of the variable amplifier, since the attenuators AT1 · AT2 to inputs of these unit amplifier section is inserted, an indication of just linearity correspondingly Certain IIP3 characteristics are improved. Further, it is possible to improve the linearity of these unit amplifying units by applying negative feedback to the transistors Q2 and Q3, and reducing the emitter area of the transistors Q2 and Q3 to increase the current density. That is, if the noise characteristics are not so important, the linearity of these unit amplifying units can be improved even if the current flowing through the transistors Q2 and Q3 is reduced.

Variable amplifier of the present embodiment, in the variable amplifier of the third embodiment shown in FIG. 12, the base current control circuit 1 shown in FIG. 2 is obtained by changing the base current control circuit 11 shown in FIG. 13, the other Has the same configuration as the variable amplifier of the third embodiment.

As shown in FIG. 13 , the base current control circuit 11 is different from the base current control circuit 1 shown in FIG. 2 in that a mirror circuit composed of a transistor Qb1c and a transistor Qb1m is provided between a transistor Qb1 and a terminal Ib1. A mirror circuit composed of transistor Qb2c and transistor Qb2m is inserted between Qb3 and terminal Ib2, and a mirror circuit composed of transistor Qb3c and transistor Qb3m is inserted between transistor Qb4 and terminal Ib3. is there. These transistors Qb1c, Qb1m, Qb2c, Qb2m, Qb3c, and Qb3m are all p-type field effect transistors (p-channel MOS transistors).

In the base current control circuit 11 shown in FIG. 13 , unlike the base current control circuit 1 in FIG. 1 in which the total base current is kept constant, by adjusting the gate width of the transistors Qb1m, Qb2m, and Qb3m, Base currents Ib1, Ib2, and Ib3 flowing in Q2 and Q3 can be adjusted independently and freely. The base current control circuit 11 then adjusts the base current so that the total consumption current of the transistors Q1, Q2, and Q3 changes according to the change in the ratio of the base currents Ib1, Ib2, and Ib3 flowing through the transistors Q1, Q2, and Q3. The currents Ib1, Ib2, and Ib are controlled.

For example, since IIP3 and the collector current are substantially proportional to each other, IIP3 at the same collector current can be improved by 3 dB by adding the emitter resistors Re2 and Re3 in FIG. 12 to the variable amplifier in FIG. If it is possible, the equivalent IIP3 can be maintained even if the collector currents of the transistors Q2 and Q3 are halved with respect to the variable amplifier of FIG. Therefore, in this case, for example, the base currents Ib1 and Ib3 flowing in the transistors Q1 and Q3 may be controlled so that the maximum value of the collector current of the transistor Q3 is ½ of the maximum value of the collector current of the transistor Q1. With such a setting, when the input power is small and high sensitivity is required, that is, when the ratio of the base current Ib1 to the base current Ib3 is large, an appropriate consumption current flows through the transistors Q1, Q2, and Q3. However, when the input power is large, that is, when the ratio of the base current Ib1 to the base current Ib3 is small, the total current consumed by the transistors Q1, Q2, and Q3 can be further reduced. In this case, for example, when the ratio of the base current Ib1 to the total base current is 100%, the current consumption of the transistors Q1, Q2, and Q3 is equivalent to that of the variable amplifier of FIG. When the ratio is 100%, it becomes 1/2 of the variable amplifier of FIG.

  In addition, the device in which the variable amplifier is used has a large input power while the use of IIP3, which is required when the input power is small, is not so strict due to the circuit design and the high gain is not required. If the device requires a high IIP3, the current consumption should be reduced when the input power is small, and the current consumption should be increased to some extent when the IIP3 with a large input power is required. Is also possible.

In this embodiment, the simplest grounded-emitter circuit corresponding to Reference Embodiment 1 is used. However, as in Reference Embodiments 1 to 3 and Embodiments 1 and 2 , a cascade connection or a base voltage control circuit is used. It is possible to further improve the characteristics by devising.

  Note that in the conventional circuits disclosed in Non-Patent Document 1 and Non-Patent Document 2, the circuit that performs the switching control and the circuit that determines the total current are independent, so the power consumption can be adjusted according to the performance. Can not.

As described above, the variable amplifier according to the present embodiment is the same as the variable amplifier according to any one of Reference Embodiments 1 to 3 and Embodiments 1 to 3 , but the current consumption (collector) of each transistor of the first group. Current). As a result, the current consumption can be adjusted according to the characteristics. Thereby, the current consumption of the entire amplifier can be reduced.

[Embodiment 5 ]
If described with reference to FIG. 14, another embodiment of the present invention is as follows. For convenience of explanation, members having the same functions as those shown in any of Reference Embodiments 1 to 3 and Embodiments 1 to 4 are denoted by the same reference numerals, and description thereof is omitted. .

FIG. 14 shows a block diagram of a portable radio terminal (such as a cellular phone) using the variable amplifier shown in the embodiments so far as a high frequency gain variable amplifier (RFVGA). As shown in FIG. 14 , the portable wireless terminal 10 of this embodiment includes an antenna 16, a band-pass filter (BPF) 17 that receives a high-frequency signal received by the antenna 16 and limits the band of the high-frequency signal, and a band By mixing the high frequency gain variable amplifier (RFVGA) 12 that amplifies the high frequency signal band-limited by the pass filter 17 and the high frequency signal amplified by the high frequency gain variable amplifier 12 with the oscillation signal of the voltage controlled oscillator (VCO) 14. A mixer (MIX) 13 for converting to a baseband signal and a demodulator (DEMOD) 15 for demodulating the baseband signal to restore the original signal are provided. The high-frequency gain variable amplifier 12 is the variable amplifier according to any one of the first to third embodiments and the first to fourth embodiments.

  The portable radio terminal 10 having the above configuration can directly connect a band pass filter (BPF) 17 to the input of the high frequency gain variable amplifier by using the high frequency gain variable amplifier 12 according to the present invention as the high frequency gain variable amplifier. The balun required for the portable radio terminal using the differential amplifier circuit is not necessary. By eliminating the balun, not only the size of the entire circuit of the portable wireless terminal can be reduced, but also a decrease in received power due to a balun loss can be prevented. Therefore, by using the high-frequency gain variable amplifier 12 according to the present invention, it is possible to realize a portable radio terminal 10 that is small and has high sensitivity.

  Furthermore, since the variable gain amplifier 12 according to the present invention can optimize the relationship between gain and current consumption according to the characteristics of the portable radio terminal, the portable radio terminal can be used for a long time with low power consumption. Can be realized.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments can be obtained by appropriately combining technical means disclosed in different embodiments. The form is also included in the technical scope of the present invention.

  The variable amplifier of the present invention can be used as an amplifier for a received signal of a portable radio terminal. The portable wireless terminal of the present invention can be used for a terminal of a wireless communication system using a high frequency such as a mobile phone.

It is a circuit diagram which shows the structure of the variable amplifier concerning the reference form of this invention. It is a circuit diagram which shows the structure of the base current control circuit with which the said variable amplifier is provided. It is a graph which shows the change of the base current of three transistors with respect to control voltage in the said variable amplifier. It is a graph which shows the gain of the whole variable amplifier with respect to a control voltage, and the change of IIP3 in the said variable amplifier. It is a circuit diagram which shows the modification of the variable amplifier concerning the said reference form. 4 is a graph showing a comparison of gain frequency characteristics between the variable amplifier of FIG. 1 and the variable amplifier of Reference Embodiment 2 . It is a graph which shows the comparison of the control voltage dependence of the gain and IIP3 characteristic of the variable amplifier of reference form 2 and the variable amplifier of reference form 3 . It is a circuit diagram showing a configuration of a base voltage control circuit variable amplifier is provided according to the implementation of the embodiment of the present invention. 9 is a graph showing the control voltage dependence of the base voltage of a grounded-emitter transistor and the base voltage of a grounded-base transistor in a variable amplifier including the base voltage control circuit shown in FIG. It is a graph which shows the control voltage dependence of the base voltage of the transistor of an emitter grounding, and the base voltage of the transistor of a grounded base in the variable amplifier which concerns on other embodiment of this invention. FIG. 11 is a graph showing a comparison of gain and IIP3 characteristic control voltage dependence of a variable amplifier including the base voltage control circuit shown in FIG. 8 and a variable amplifier having the characteristic shown in FIG. 10 . It is a circuit diagram which shows the structure of the variable amplifier concerning further another embodiment of this invention. FIG. 6 is a circuit diagram showing a configuration of a base current control circuit that controls a base current of a transistor with a common emitter in a variable amplifier according to still another embodiment of the present invention. It is a block diagram which shows the structure of the portable radio | wireless terminal using the variable amplifier of this invention.

Explanation of symbols

1 Base current control circuit (base current control unit)
2 Base voltage control circuit (voltage control unit)
11 Base current control circuit (base current control unit)
12 High frequency gain variable amplifier (variable amplifier)
13 Mixer 14 Voltage Control Oscillator 15 Demodulator 16 Antenna 17 Band Pass Filter Q1 Transistor (Bipolar Transistor)
Q2 transistor (bipolar transistor)
Q3 transistor (bipolar transistor)
Q4 transistor (additional transistor)
Q41 Transistor (additional transistor)
Q42 Transistor (additional transistor)
Q43 Transistor (additional transistor)
RL resistor (load)
AT1 attenuator AT2 attenuator AT3 attenuator AT4 attenuator

Claims (3)

The emitter of the additional bipolar transistor has a plurality of cascaded unit amplification stages connected to the collector of a grounded-emitter bipolar transistor whose base is the signal input end,
The signal input terminals of the unit amplification stages are sequentially connected in series via an attenuator, and the output of the unit amplification stage is an amplification unit connected to a common load;
A base current control unit for controlling a current flowing through the base of each of the grounded emitter bipolar transistors;
A base voltage control unit for controlling the base voltage of each of the additional bipolar transistors,
The variable amplifier according to claim 1, wherein when the current flowing into the base of the common emitter bipolar transistor is equal to or less than a predetermined current value, the base voltage of the additional transistor approaches 0V . The source of the additional field effect transistor has a plurality of cascaded unit amplification stages connected to the collector of a grounded-emitter bipolar transistor having the base as a signal input end,
The signal input terminals of the unit amplification stages are sequentially connected in series via an attenuator, and the output of the unit amplification stage is an amplification unit connected to a common load;
  A base current control unit for controlling a current flowing through the base of each of the grounded emitter bipolar transistors;
  A gate voltage control unit for controlling the gate voltage of each of the additional field effect transistors,
  The variable amplifier according to claim 1, wherein when the current flowing into the base of the common-emitter bipolar transistor is equal to or lower than a predetermined current value, the gate voltage of the additional transistor approaches 0V. A portable radio terminal comprising an amplifier for amplifying a received signal, wherein the amplifier is the variable amplifier according to claim 1.

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