JPS6036022B2 - Voltage-current converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage-current converter, and uses transistors having different junction layer structures (or channels) each having a constant voltage source connected between their bases (or gates). A voltage-current converter that has a small current value at which both output currents of transistors match, can accurately obtain complementary voltage-current conversion characteristics with a predetermined slope, and is suitable for integration into an integrated circuit. The purpose is to provide.

In recent years, with the development of small products such as microcassettes and thin radios, there has been a demand for internal circuits that do not take up much space and that operate at low voltages. To meet this requirement, particularly low supply voltages (e.g. 1.5
It became necessary to develop integrated circuits for power amplifiers that could operate at low voltages (up to about V), and a voltage-to-current converter that could operate at low voltages was needed to drive them. Figure 1 shows conventional voltages that can be used for the above applications.
A circuit diagram of an example of a current converter is shown.

In the figure, NPN transistors Qo, , Q2 constitute a difference amplifier, and their collectors and collector load resistance R
o, , of the PNP transistor Q at the connection point with Ro2,
The base of Q is connected. Above transistor Q
. , , the input voltage applied to the base of False 2 causes a current i. , i2 and output. The input voltage versus output current characteristics are complementary, as shown in FIG. 2, and the current value 1 at their intersection is relatively low. When this voltage-current converter is applied to the power intensifier described above, by setting the current value 1 as the idling current, a large current gain can be obtained when a large signal is input.

However, the above conventional converter has transistors Q3 and Q
As can be seen from the general base voltage vs. collector current characteristics of transistors, the ratio of the variation in the output currents i, , i2 to the variation in the base voltage of 4 is extremely large. extremely difficult to set up,
When applied to the above power amplifier, resistors Ro・, Ro2
However, there were drawbacks such as the need for highly accurate transistors Q3, Q4, etc.

The present invention eliminates the above-mentioned drawbacks, and one embodiment thereof will be described with reference to FIGS. 3 to 5.

FIG. 3 shows a circuit diagram of an embodiment of a voltage-current converter according to the present invention.

In the figure, 1 is a voltage input terminal, and Q, , Q2 are NPN transistors and PNP transistors for voltage-current conversion. An NPN transistor Q3 whose collector and base are short-circuited and connected as a diode is connected between the bases of the transistors Q, Q2. Further, a diode-connected PNP transistor Q is connected between the emitters of the transistors Q, Q2. NPN transistors Q5 and Q6 constitute a differential amplifier circuit, and the base of Q6 is connected to input terminal 1,
It is connected to a constant voltage source 2 that outputs a reference voltage V^.
The collector of the transistor Q is connected to the collector and base of a PNP transistor Q7 whose base and collector are short-circuited, and the collector of the transistor Q5 is connected to the base and collector of the transistor Q4. The base and emitter of the above transistor Q7 are PN
It is commonly connected to the base and emitter of the P transistor Q, forming a current mirror circuit.

The collector of the output side transistor Q8 of this current mirror circuit is connected to the emitter of the transistor Q2 and the emitter of the transistor Q, respectively. Also, the transistor Q3
The base and collector of Q3 are connected to the power supply voltage (10Vcc) input terminal via a resistor R, and the emitter of Q3 has a constant current of 1. , is grounded via a constant current source 3 that outputs , and on the other hand,
The emitters of the transistors Q and Q6 are grounded via a constant current source 4 which outputs a constant current of 2. Next, the operation of the above-mentioned constituent circuit will be explained.

The collector current of the above transistors Q,,Q2 is 1,,1
2. Also, the collector current of transistors Q8 and Q4 is
13 and 14 as shown in the figure. Further, transistors Q7 and Q8 have the same characteristics, and the collector current of transistor Q7 is the current 131
Almost equal. On the other hand, the sum of the collector current of transistor Q7 and the above-mentioned current L is always equal to constant current L2. Therefore,
For currents 13 and 14, 13 + 14 = L2
The relationship [1} always holds true. Further, the base-emitter potential Vo of the diode-connected transistor Q is kept at a constant voltage by a constant current source 3.

Now, assuming that the differential amplifier circuit consisting of transistors Q5 and Q is in a balanced state, the collector currents of transistor Q5 and the transistor are equal, so 13=14
[2] The following relationship holds true.

Therefore, at this time, the output currents 11 and 12 from the transistors Q, , Q2 become 11=12=, and the circuit is balanced.

Next, as the input voltage V, becomes larger than the value V in the above-mentioned equilibrium state, the current 14 becomes, and as is clear from equation {1), the current 13 becomes smaller, so the difference between them is Current flows through the connection points on both sides of the diode-connected transistor Q4, and the output current 1 becomes large and the output current 12 becomes small.

Conversely, as the input voltage V becomes smaller than the value in the above equilibrium state, the current 13 becomes larger and the current L becomes smaller, and contrary to the above, the output current 1 becomes smaller and the output current 12 becomes larger. Become.
In this way, the voltage-to-current converted currents 1, 12 taken out from the collectors of the transistors Q, , Q2 become complementary to each other. Further, in the circuit shown in FIG. 3, transistors Q, . Q2 base-emitter voltage VB
o,,VBG2 and the base-to-emitter voltages Vo,,Vo2 of the transistors Q, can be expressed by the following equation. VBB, 10VBE2 = VD, 10VD2 Potato (1 Manabu Sakuragawa) = Shen n sen.

2 '3' becomes.

However, [3} in formula 1: PN of transistors Q3 and Q4
Reverse saturation current of the junction, q: electron charge, k: Bormann constant, T: absolute temperature of the PN junction of the transistors Q3 and Q4. Therefore, reduce the value of constant electric current 8o by 4,
By selecting a large value for the constant current lo2, the output currents (=1, =12) when the differential amplifier circuit consisting of the transistor method and Q is in a balanced state become small, and the differential amplifier circuit becomes unbalanced. When a balanced state is achieved (such as when an alternating current voltage is applied to the input terminal 1), a large current gain can be obtained.

The relationship between the input voltage V and the output currents 1, 12 is as shown in FIG. In this embodiment, the above-mentioned current values can be determined by adjusting the constant current sources 3 and 4, so that the current value when the differential amplifier circuit is in a balanced state can be easily and accurately reduced to a small value L'. Can be set. Note that since the transistors Q and Q and Q2 and Q4 each have the same junction layer structure, temperature compensation can be performed and it is suitable for integration into an integrated circuit (IC). FIG. 5 shows a circuit diagram when the converter of the present invention is applied to a drive circuit of a power amplifier. In the figure, the same parts as in FIG. 3 are given the same reference numerals, and their explanations will be omitted. The collector of transistor Q, is PNP transistor Q and Q,. The base and collector of the input transistor Q9 of a current mirror circuit are connected to the outside. The collectors of the output transistors Q, o of this current mirror circuit are NPN power transistors Q, . connected to the base of.
On the other hand, the collector of the transistor Q2 is grounded via the resistor R3, and the collector of the NPN type power transistor Q
, 2 is supported. power transistor Q
、． The emitters of the power transistors Q, . . . and the collectors of the power transistors Q, . Transistors Q and Q. are commonly connected to the emitters of o. Further, the output terminal 5 is negatively fed back to an input voltage amplifier stage (not shown) via a resistor R4. In the above circuit, among the output currents 1, 12 taken out after voltage-current conversion, 1. are transistors Q and Q,

Power transistors Q, . 12 is a power transistor Q,
2 directly. As a result, the AC voltage input to the input terminal 1 has its positive polarity or negative polarity part connected to the power transistors Q, . Alternatively, the power is amplified by Q and Q2, respectively, and output from the output terminal 5. Here, when no AC voltage is applied to input terminal 1, the transistor wire and Q
It is preset that a DC voltage is applied that will bring the differential amplifier consisting of 6 into a balanced state. Therefore, when the input AC voltage does not come in, the output current from the collectors of the transistors Q, Q2 is the small current value lo, and if this is taken as the idling current, the input When a large amplitude AC voltage enters terminal 1,
It can be seen that a large current gain can be obtained. When no AC voltage is applied to the input terminal 1, the bootstrap capacitor C is charged by the power supply voltage applied via the resistor R2. Furthermore, if the power supply voltage is 1.5V or higher, this voltage-current converter operates, so power transistors Q, . I can drive the Q12 well.

Note that by providing a current mirror circuit on the output side of the transistor Q2 and providing a current gain to this current mirror circuit and the current mirror circuit provided on the output side of the transistor Q, an even larger current can be applied to the power transistor Q. 、． ,Q,2. In the above embodiment, bipolar transistors having mutually different junction layer structures were used as Q, Q2, but the present invention is not limited to this, and P-channel and N-channel field effect transistors may be used, respectively. can.

Further, the transistors Q3 and Q4 may be diodes. Further, the converter of the present invention can be applied to a power amplifier other than the power amplifier as explained in FIG. 1” amplifier, operational amplifier, etc.

As described above, the voltage-to-current converter according to the present invention includes a first transistor such as a transistor or a diode in which a diode is connected between the bases (or gates) of the first and second transistors having different junction layer structures (or channels). A second diode, such as a transistor or a diode, which is diode-connected between the emitters (or sources or drains) of the first and second transistors;
The first diode element is connected to a constant current source to form a constant voltage source, and one of the connection points on both sides of the second diode element is connected to a current mirror circuit, and the other is connected to a current mirror circuit. It is connected to the output side of one of the two transistors that make up the differential amplifier circuit, and the input voltage is supplied to the input terminal of one of the two transistors that make up the differential amplifier circuit, and the reference voltage is supplied to the other input terminal. By supplying the voltage, a differential current corresponding to the input voltage with respect to the reference voltage is caused to flow from the differential amplifier circuit to the connection points on both sides of the second diode element, and the input voltage is applied to the first and second diode elements.
Since the current is converted into a current and output from at least one of the collectors (or drains or sources) of the first and second transistors, the values of the output currents from the collectors (or drains or sources) of the first and second transistors are both the same. The current value lo when they match is relatively small, and complementary input voltage vs. output current characteristics can be accurately obtained,
It can operate even at low voltages (for example, 2 V or less), and the configuration of the diode-connected transistor and the constant voltage source allows temperature compensation, so it is possible to have a wide stable operating range with respect to temperature, and the constant voltage source By using a constant current source and a diode-connected transistor, the current value lo can be adjusted using the current of the constant current source, so that the current value 1 can be easily and accurately adjusted.

can be set, and because it has a DC coupling configuration, it is suitable for integrated circuits.For example, when applied to a drive circuit of a power amplifier, by setting the above current value lo as an idling current, the current gain can be made sufficiently large. can be taken,
Furthermore, since the power transistor can be driven with a low voltage, it has many advantages such as being extremely advantageous when operated with a battery.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of an example of a secondary voltage-current converter, Figure 2
The figure shows an example of the input voltage vs. output current characteristics in Figure 1.
FIG. 3 is a circuit diagram showing an embodiment of the converter of the present invention, FIG. 4 is a diagram showing an example of the input voltage vs. output current characteristics of FIG. 3, and FIG. FIG. 2 is a circuit diagram showing an example of application to a circuit. 1... Voltage input terminal, 2... Constant voltage source, 3, 4...
- Constant current source, 5... Output terminal, 1,, 12... Output current, Q. ...NPN transistor for voltage-current conversion, Q2...PNP transistor for voltage-current conversion, Q
5, Q...NPN transistors forming a differential amplifier circuit, Q, . ,Q,2・”Power transistor. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5

Claims (1)

[Claims] 1. The first layer has a different bonding layer structure (or channel) from each other.
and a first diode element such as a diode-connected transistor or diode between the base (or gate) of the second transistor, and between the emitter (or source or drain) of the first and second transistor. A second diode element such as a diode-connected transistor or diode is connected to the terminal, the first diode element is connected to a constant current source to constitute a constant voltage source, and the connection on both sides of the second diode element is made. One of the points is connected to the current mirror circuit, and the other is connected to the output side of one of the two transistors forming the differential amplifier circuit, and the input terminal of one of the two transistors forming the differential amplifier circuit. By supplying an input voltage to and a reference voltage to the other input terminal, the differential amplifier circuit generates a differential current corresponding to the input voltage with respect to the reference voltage across both sides of the second diode element. , and the input voltage is converted into a current and outputted from at least one of the collectors (or drains or sources) of the first and second transistors. converter.