JP3036221B2 - Semiconductor integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal amplification circuit. In particular, a signal amplifier I which has a wide output voltage range, reduces idle current, and enables stable amplification even in a high temperature environment.
Regarding C.

[0002]

2. Description of the Related Art Heretofore, there has been known a so-called push-pull type output circuit in which emitters of pnp type and npn type transistors are connected to each other and an output is taken out from the connection point. FIG. 7 shows a partial circuit diagram of a semiconductor integrated circuit having such a push-pull type output circuit.

In a push-pull type output circuit as shown in FIG. 7, the transistor Qo1 of the output circuit is cut off before the output voltage reaches the vicinity of the power supply voltage level. Cannot be amplified. That is, the transistor Qo1 normally has a voltage between the base voltage and the emitter voltage of 0.6.
An offset voltage of about volts (hereinafter referred to as VBE) is required. Therefore, this circuit can only output a voltage lower than the power supply voltage by VBE volts.

In order to solve such a problem, conventionally,
A circuit as shown in FIG. 8 is used. FIG.
Is a circuit provided with a constant current power supply 10 instead of the transistor Qo1, and according to this circuit,
It is possible to swing the output voltage up to the power supply voltage.

However, the circuit shown in FIG. 8 has a drawback that the constant current power supply 10 always supplies a current irrespective of the presence or absence of a signal, so that the reactive current is large. That is, even when little current flows through the load 12, the constant current power supply 10 continues to flow a constant current, and that current must be consumed in the transistor Qo2.

The circuit shown in FIG. 9 is a circuit provided with a constant current power supply 14 instead of the transistor Qo2. According to this circuit, the output voltage can be changed to the ground potential (0 volt). It is possible. The circuit shown in FIG. 9 is based on the same principle as that of the circuit shown in FIG. The circuit shown in FIG. 9 has the same problem as the circuit shown in FIG.

Further, the circuit shown in FIG. 9 has a problem peculiar to the circuit in practical terms. This problem will be described with reference to FIG. FIG. 10 shows a specific example of a circuit which is capable of outputting an output voltage up to the ground potential using a constant current power supply as in FIG. The constant current source indicated by IR5 in the figure is a newly added constant current source. In such a circuit, when the output voltage approaches the ground voltage, the transistor Q9 in the figure is cut off this time. The transistor Q9 drives a push-pull circuit including the transistors Q10 and Q11. When the transistor Q9 is cut off, the feedback loop is completely broken. As a result, the output voltage cannot swing from ground to VBE volts.

For the reasons described above, in recent years, a circuit as shown in FIG. 11 has been frequently used. The circuit shown in FIG. 11 is a circuit using a bootstrap. This circuit eliminates the voltage loss caused by the VBE of the transistor Qo1 by increasing the power supply voltage of the base potential of the transistor Qo1.

A configuration for improving the power efficiency of a push-pull type output circuit is disclosed in, for example, JP-A-59-21.
There is an example described in Japanese Patent Publication No. 105-105. The amplifier circuit described here detects the output signal and changes the power supply voltage accordingly. With such a configuration, a highly efficient amplifier circuit is realized.

[0010]

The above-mentioned bootstrap generally requires a large-capacity capacitor, and therefore, an aluminum electrolytic capacitor is exclusively used. Since this electrolytic capacitor is vulnerable to high temperatures, it becomes difficult to use it in a high temperature environment. Further, a large-capacity electrolytic capacitor has a problem that the volume is large and the device cannot be miniaturized.

As described above, in a device such as an in-vehicle electronic device which is required to be small in size and low in power consumption and must be kept at a high temperature, the above-mentioned means should be employed. Could not. Therefore, in an amplifier circuit of one power supply, the output voltage is only a voltage in the range from {power supply voltage −VBE} to {VBE}. Also, in the output amplifier circuit of the two power supplies, the output voltage is changed from {+ power supply voltage−VBE} to {−power supply voltage +
The voltage can only be in the range up to VBE｝. That is, the voltage cannot be used effectively.

Therefore, for example, in a low-voltage driven circuit such as a battery-driven amplifier circuit or a vehicle-mounted amplifier circuit, there is a problem that the waste of voltage efficiency cannot be ignored and a so-called dynamic range cannot be sufficiently obtained. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a semiconductor integrated circuit capable of changing an output voltage to a voltage substantially equal to a power supply voltage.

[0014]

According to a first aspect of the present invention, there is provided an output circuit including an emitter follower-connected transistor in a semiconductor integrated circuit. A high-potential dynamic range enlarging circuit, wherein the high-potential dynamic range enlarging circuit detects that the voltage of the output terminal to which the emitter of the transistor is connected is higher than a predetermined high threshold voltage. Potential detection means,
Current supply means for supplying a current from the output terminal if the high potential is detected by the high potential detection means, wherein the low potential dynamic range expansion circuit has a voltage at the output terminal Low-potential detecting means for detecting that the potential is lower than the low threshold voltage, and if the low potential is detected by the low-potential detecting means,
And a current sink for extracting a current from the output terminal.

The high-potential dynamic range expansion circuit includes a high-potential detecting means for detecting that the voltage of the output terminal is higher than a predetermined high threshold voltage, and a high-potential detecting means for detecting the voltage of the output terminal. If it is detected that the voltage is higher than the predetermined high threshold voltage,
Current supply means for supplying a current from the output terminal. Therefore, even if the output transistor is cut off, current can be supplied from the output terminal.

Further, the low-potential dynamic range expansion circuit includes a low-potential detecting means for detecting that the voltage of the output terminal is lower than a predetermined low threshold voltage, and the low-potential detecting means detects the voltage of the output terminal. Is detected to be lower than the predetermined low threshold voltage,
Current sink means for extracting a current from the output terminal. Therefore, even if the output transistor is cut off, current can be drawn from the output terminal.

According to a second aspect of the present invention, there is provided an output circuit including a push-pull circuit including two transistors, a diode connected between bases of the two transistors, and a diode connected to one end of the diode. And
A first npn transistor driving the output circuit;
In a semiconductor integrated circuit having a low-potential dynamic range expansion circuit, the semiconductor integrated circuit is connected to the other end of the diode,
A low-potential dynamic range expansion circuit that includes a second npn transistor that drives the output circuit, wherein the low-potential dynamic range expansion circuit detects that the voltage at the output terminal is lower than a predetermined low threshold voltage; And a current sink for extracting a current from the output terminal when the low potential is detected by the low potential detecting means.

Therefore, even if the output voltage becomes close to the ground voltage and the first npn transistor is cut off,
The output transistor can be driven by the second npn transistor.

[0019]

The high potential dynamic range expansion circuit according to the first aspect of the present invention supplies a current to the output terminal when the output voltage reaches the vicinity of the power supply voltage in the case of one power supply. Therefore, even if the output voltage becomes substantially equal to the power supply voltage, the feedback loop is not interrupted.

The low potential dynamic range expansion circuit according to the first aspect of the present invention extracts a current from the output terminal when the output voltage reaches the vicinity of the ground voltage in the case of one power supply. Therefore, even if the output voltage becomes substantially equal to the ground voltage, the feedback loop does not break.

Furthermore, the second np in the second invention
The n-transistor has its collector connected to the other end of the diode to which the collector of the first transistor is connected. Therefore, in the case of one power supply, even if the output voltage reaches the vicinity of the ground voltage and the first npn transistor driving the output circuit is cut off, the second n
Since the pn transistor drives the output circuit without being cut off, the feedback loop is not interrupted.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The examples described in the text are all 1
The present invention relates to a power supply semiconductor integrated circuit.

FIG. 1 is a block diagram showing the configuration of a semiconductor integrated circuit according to a first preferred embodiment of the present invention. FIG.
As shown in FIG. 5, in this embodiment, the output voltage detection circuit 20 monitors the output voltage and detects whether the output voltage has become higher than the power supply voltage Vcc-VBE.
As a result, if the output voltage is higher than Vcc-VBE, the constant current source 22 is controlled to supply a predetermined current to the output terminal.

FIG. 2 is a specific circuit diagram including the output voltage detection circuit 20 and the constant current source 22. As shown in the figure, the output voltage detection circuit 22a includes a high potential threshold Vth set from the resistors R3 and R4,
The output voltage of the amplifier circuit 24 is compared. If the output voltage is higher, the constant current source 22a, which is a current mirror circuit, is driven to supply a current to the output terminal 26.

The amplifying circuit 24 has exactly the same configuration as the conventional amplifying circuit, and its output circuit includes a transistor Q.
10 and Q11. The output voltage detection circuit 22a is composed of a differential amplifier that compares the high potential threshold Vth with the output voltage. This differential amplifier comprises transistors Q12 to Q1
It consists of 15 transistors. The high potential threshold Vth is set to Vcc-VBE. That is, when the output voltage becomes higher than Vcc-VBE, the collector current of the transistor Q14 increases. Transistor Q
Since transistor 14 and transistor Q16 are connected in series, the current flowing through transistor Q16 forming constant current source 22a also increases. As a result, a current proportional to the transistor Q16 flows through the other transistor Q17 forming the current mirror circuit, and this proportional current is supplied to the output terminal. In this embodiment, the emitter area of the transistor Q17 is set to be five times as large as that of the transistor Q16, and a current five times the current flowing through the transistor Q16 is supplied to the output terminal through the transistor Q17.

That is, the current flowing through the transistor Q16 is only 1/5 of the current supplied from the transistor Q17 to the output terminal 26, so that the idle current can be reduced. In the present embodiment, the emitter area ratio of Q17 and Q16 is set to five times, but the present invention is not limited to this, and the effect of reducing the idle current increases as the ratio increases.

What is characteristic in this embodiment is that even when the output voltage becomes equal to or higher than Vcc-VBE, the constant current source 22a
Supplies a current to the output terminal 26, so that the output voltage is Vcc
That is, the feedback loop is not interrupted even when the voltage exceeds -VBE. Therefore, it is possible to swing the output voltage almost to the power supply voltage.

FIG. 3 shows the state of the output voltage of the semiconductor integrated circuit according to this embodiment. FIG. 3A is a graph of the output voltage of the conventional semiconductor integrated circuit. As shown in the figure, an output voltage higher than the power supply voltage Vcc-VBE cannot be obtained. When the above signal was input, the output signal was clipped. On the other hand, FIG.
(B) is a graph of the output voltage of the semiconductor integrated circuit according to the present embodiment. As shown in the figure, since it is possible to obtain an output voltage higher than the power supply voltage Vcc-VBE, the output signal is not clipped,
The input signal is faithfully reproduced up to the power supply voltage. In addition,
In the graph of FIG. 3, the horizontal axis is the time axis, and the vertical axis is the output voltage.

FIG. 4 is a block diagram showing the configuration of a semiconductor integrated circuit according to a second preferred embodiment of the present invention. FIG.
As shown in FIG. 5, in the present embodiment, the output voltage detection circuit 40 monitors the output voltage, and
It detects whether it has become smaller than BE. As a result, if the output voltage is smaller than VBE, the constant current source 42 is controlled to extract a predetermined current from the output terminal.

FIG. 5 is a specific circuit diagram including the output voltage detection circuit 40 and the constant current source 42. As shown in the figure, the output voltage detection circuit 40a includes a low-potential threshold −V set by a resistor R43 and a resistor R44.
th and the output voltage of the amplifier circuit 44 are compared. If the output voltage is higher, the constant current source 42a, which is a current mirror circuit, is driven to supply a current to the output terminal 46.

The amplifier circuit 44 is newly provided with a transistor Q
9 'and its base resistor R2' are added, and the configuration is exactly the same as that of the conventional amplifying circuit. The output circuit includes a push-pull circuit composed of transistors Q10 and Q11 as in the first embodiment. Has become. And
The output voltage detection circuit 42a includes a differential amplifier that compares the low potential threshold value -Vth with the output voltage. This differential amplifier is composed of transistors Q52 to Q55. In addition, the low potential threshold −Vth
Is set to VBE. That is, when the output voltage becomes lower than VBE, the collector current of transistor Q54 increases. Since transistor Q54 and transistor Q56 are connected in series, the current flowing through transistor Q56 forming constant current source 42a also increases. As a result, a current proportional to the transistor Q56 flows through the other transistor Q57 forming the current mirror circuit, and this proportional current is drawn from the output terminal. In this embodiment, the emitter area of the transistor Q57 is set to five times that of the transistor Q56.
Five times the current flowing through the transistor Q56 is supplied to the output terminal through the transistor Q57.

That is, the current flowing through the transistor Q56 is only 1/5 of the current supplied from the transistor Q57 to the output terminal 26, and the idle current can be reduced. The emitter area ratio between the transistors Q57 and Q56 is not limited to five times.

What is characteristic in this embodiment is that even when the output voltage is lower than VBE, the constant current source 42a draws a current from the output terminal 46, so that even when the output voltage becomes lower than VBE, a feedback loop is formed. There is no interruption. Therefore, the output voltage is almost equal to the ground voltage (0
Bolts).

FIG. 6 shows the state of the output voltage of the semiconductor integrated circuit according to this embodiment. FIG. 6A shows the state of the output voltage of a conventional semiconductor integrated circuit.
As shown in the figure, since an output voltage lower than VBE cannot be obtained, when a signal lower than VBE is input, the output signal is clipped. On the other hand, FIG. 6B shows the state of the output voltage of the semiconductor integrated circuit according to the present embodiment. As shown in the figure, since an output voltage equal to or lower than VBE can be obtained, the output signal is not clipped and the input signal is faithfully reproduced up to the ground voltage. The horizontal axis of the graph shown in FIG. 6 is a time axis, and the vertical axis is an output voltage.

As described above, according to the present embodiment, when the output voltage approaches the power supply voltage by using the constant current source, the current is supplied to the output terminal. It is possible.

Similarly, when the output voltage approaches the ground voltage using the constant current source, the current is drawn from the output terminal, so that the output voltage can be changed to the ground voltage.

Furthermore, in this case, in particular, the bases of the transistors constituting the push-pull circuit are connected by a diode, and np having a collector connected to one end of the diode.
When the push-pull circuit is driven using the npn transistor, the np transistor drives the push-pull circuit even if the current is drawn as described above.
The n transistor is cut off. In the present embodiment, as described above, since the second npn transistor having the collector connected to the other end of the diode is provided, it is possible to continue driving the push-pull circuit.

In this embodiment, only one power supply has been described. However, the present invention can be similarly applied to a semiconductor integrated circuit having two power supplies. Further, the case where the current is supplied (the first embodiment) and the case where the current is drawn (the second embodiment) are described separately, but it is also preferable to apply both circuits simultaneously.

[0039]

As described above, according to the present invention, in the case of one power supply, the high-potential dynamic range expansion circuit enables the output voltage to be varied up to the power supply voltage. It is possible to obtain a circuit.

Similarly, in the case of one power supply, the low-potential dynamic range expansion circuit enables the output voltage to swing to the ground voltage, so that it is possible to obtain a semiconductor integrated circuit with an expanded dynamic range.

Further, np for driving the push-pull circuit
Since it has a second npn transistor whose collector is connected to the other end of the diode to which the collector of the n transistor is connected, even if the first npn transistor is cut off, the push-pull circuit can be used. It can keep driving. As a result, there is an effect that a semiconductor integrated circuit which can swing the output voltage to near the ground potential can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a semiconductor integrated circuit according to a first preferred embodiment of the present invention;

FIG. 2 is a circuit diagram illustrating a specific circuit example of the semiconductor integrated circuit of FIG.

FIG. 3 is a graph showing an operation of the semiconductor integrated circuit of FIG. 2;

FIG. 4 is a configuration block diagram of a semiconductor integrated circuit according to a second preferred embodiment of the present invention;

FIG. 5 is a circuit diagram illustrating a specific circuit example of the semiconductor integrated circuit of FIG.

FIG. 6 is a graph showing an operation of the semiconductor integrated circuit of FIG. 5;

FIG. 7 is a partial circuit diagram of a semiconductor integrated circuit having a conventional push-pull circuit.

8 is a partial circuit diagram when one of the transistors constituting the push-pull circuit of FIG. 7 is replaced with a constant current source.

9 is a partial circuit diagram when the other of the transistors constituting the push-pull circuit of FIG. 7 is replaced with a constant current source.

FIG. 10 shows a conventional push-pull circuit including a constant current source IR5.
FIG. 9 is a circuit diagram for explaining that a drive transistor Q9 is cut off when a current is drawn out from an output terminal by adding "."

FIG. 11 is a circuit diagram of a conventional example in which a push-pull circuit is driven by a bootstrap at a voltage higher than a power supply voltage.

[Explanation of symbols]

 20, 40 Output voltage detecting circuit 20a, 40a Output voltage detecting circuit 22, 42 Constant current source 22a, 42a Constant current source 24, 44 Amplifying circuit 26, 46 Output terminal

Claims (2)

(57) [Claims] 1. A semiconductor integrated circuit including an emitter-follower-connected transistor in an output circuit, the semiconductor integrated circuit including at least one of a high-potential dynamic range expansion circuit and a low-potential dynamic range expansion circuit; High potential detecting means for detecting that the voltage of the output terminal to which the emitter of the transistor is connected is higher than a predetermined high threshold voltage; and the high potential is detected by the high potential detecting means. And a current supply means for supplying a current from the output terminal. The low-potential dynamic range expansion circuit detects that the voltage of the output terminal is lower than a predetermined low threshold voltage. A low-potential detecting means for detecting the low potential, The semiconductor integrated circuit which comprises a current suction means for sucking the current from. 2. An output circuit including a push-pull circuit including two transistors; a diode connected between bases of the two transistors; and a drive terminal connected to one end of the diode to drive the output circuit. A semiconductor integrated circuit having a first npn transistor and a low-potential dynamic range expanding circuit, comprising: a second npn transistor connected to the other end of the diode and driving the output circuit; An enlarging circuit, a low-potential detecting unit that detects that a voltage of an output terminal of the output circuit is lower than a predetermined low threshold voltage; and And a current sink means for extracting a current from the output terminal.