JPH01106605A - Transistor circuit - Google Patents

Abstract

PURPOSE:To reduce the leakage current between collectors and emitters of transistors (TR) by connecting a diode, etc., between a collector of a TR of an input stage of a TR group of Darlington connection and a power supply. CONSTITUTION:A diode 7 is connected in the forward direction between a power terminal 6 and collectors of TRs 1, 2, 3. In injecting a current IB to an input terminal 4, a current being a multiple of (1+hFE) of the base current IB flows to the emitter of the TR 2, it becomes the base current of the TR 3, resulting that a current being a multiple of (1+hFE)X(1+hFE)X(1+hFE) of the base current IB of the TR 1 flows to the emitter of the TR 3. The collector- emitter voltage VCE of the TRs 1, 2, 3 is reduced more than the leading voltage of a collector voltage-current characteristic so as to reduce the leakage current according to the voltage drop across the diode 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a transistor circuit in which two or more transistors are connected in a Darlington manner.

2. Description of the Related Art Conventionally, this type of transistor circuit has had a configuration as shown in FIG. In Fig. 2, 1゜2.3 is a Darlington-connected NPN transistor, 4 is an input terminal connected to the base of input stage transistor 1, 5 is an output terminal connected to final stage transistor 3, and 6 is an output terminal connected to the final stage transistor 3. It is a power supply terminal connected to the collectors of all transistors 1.2.3. - Problem to be solved by the invention In such a conventional transistor circuit, when a current is injected into the input terminal 4, the base current I of the transistor 10 increases.
A current multiplied by the current amplification factor hFE of transistor 1 flows into the collector of transistor 1, and a base current 1. (1+hpg) times the current flows. The emitter current that is amplified by 1.0 (1+hrg) times the base current in transistor 1 is applied to the base of transistor 20, and the emitter current of transistor 2 that is amplified by transistor 1 (1+hpE) is applied to the emitter of transistor 2. Amplified twice, this current is applied to the base of transistor 30. The emitter current of transistor 2, which has been amplified by transistors 1 and 2, is further amplified by (1+hyg) and output to the emitter of transistor 3.

On the other hand, the relationship between the leakage current ice generated between the collector and emitter of the NPN transistor and the collector-emitter voltage VCE is as shown in FIG. VB in FIG. 3 is the voltage at which the leakage current Icg generated between the collector and emitter begins to increase rapidly when the voltage VCE between the collector and emitter is increased.

In the conventional circuit configuration shown in FIG. 2, when an extremely small current IB is applied to the input terminal 4 to operate the circuit, the transistor 1
When a leakage current occurs between the collector and emitter of
If the voltage exceeds l I in the circuit of FIG.
aX (1+hpg) +Ice) X(1+hpg)
A current of 1. Since is an extremely small current, the leakage current between the collector and emitter of transistor 1 cannot be ignored.
Affects output.

The present invention solves these conventional problems,
Prevents leakage current that occurs between the collector and emitter of the transistor, and prevents the final output from being affected by leakage current.
The present invention provides a transistor circuit with the following characteristics.

Means for Solving the Problem In order to solve this problem, the present invention connects two or more transistors in Darlington connection, and provides a voltage drop between at least the collector of the input stage transistor and the power supply or the reference voltage source. It is a combination of elements or circuit elements connected together.

Effect: With this configuration, the collector voltage of the input stage transistor is lowered to a level that does not saturate this transistor, and the collector-emitter voltage VCE is made smaller than Ve shown in Figure 3 (and the leakage current generated between the collector and emitter is reduced). By making the current negligible even when inputting an extremely small current, it is possible to prevent the influence on the output.

Embodiment FIG. 1 shows a transistor circuit according to an embodiment of the present invention, and parts having the same functions as those in FIG. 2 are denoted by the same reference numerals. The basic amplification operation is the same as the conventional example shown in FIG. A current flows and is applied to the base of transistor 2. Furthermore, the emitter of transistor 2 receives the applied base current (10h
rE) times the current, which further becomes the base current of transistor 3, and the emitter of transistor 3 has the base current IB of transistor 1 (1+hp[riX (
1+hpg) X (1+hpg) times the current flows.

As shown in FIG. 1, in this embodiment, a diode 7 is connected in the forward direction between the collectors of the transistors 1, 2.3 and the power supply terminal 60.

In this way, the voltage drop across the diode 7 causes the collector potentials of the transistors 1, 2.3 to be lower than in the conventional circuit shown in FIG. In other words, the voltage VCE between the collectors and emitters of the transistors 1, 2, and 3 becomes smaller than before, and can be made smaller than Ve shown in FIG. 3, and the leakage current can be reduced compared to the conventional circuit.

In particular, as in this embodiment, all transistors 1 and 2
．． When a diode 7 is connected between the collector of transistor 3 and the power supply terminal 6, the VCE of all the transistors becomes small (not only between the collector and emitter of transistor 1 but also between the collector and emitter of transistor 2 and 3). Since the leakage current that occurs can be reduced, it is possible to further prevent the influence on the output.

Note that it is also possible to simply insert a voltage drop element or circuit between the collector of the input stage transistor 1 and the power supply terminal 6. The leakage current between the collector and emitter of input stage transistor 1 can be reduced by reducing the leakage current between the collector and emitter of input stage transistor 1.
The emitter output of IBX (1+hrg)
The effect of preventing a current of 1+hpg) can be obtained.

Further, in the embodiment shown in FIG. 1, the diode 7 is used as a voltage drop element, but other elements such as a resistor may be used, or furthermore, a circuit element that causes a voltage drop may be used.

Furthermore, the power supply terminal 6 may be a reference voltage source. When a PNP transistor is used as the transistor, the power supply terminal 6 is grounded and the diode is connected in reverse, that is, the anode side is connected to the collector side.

Effects of the Invention As described above, according to the present invention, when the base input of the transistor in the input stage is an extremely small current and the output is obtained from the output terminal of the transistor in the final stage to which the extremely small current is input, at least the input A voltage dropping element or circuit connected between the collector of the transistor in the stage and a power supply or reference voltage source causes a voltage VCE between the collector and emitter of the transistor to be lower than vB, which is generated between the collector and emitter of the transistor. It is possible to suppress the leakage current to a negligible level compared to the input current, thereby preventing the effect on the output.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a transistor circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional transistor circuit, and FIG. 3 is a circuit diagram showing a collector-emitter voltage VCII and the voltage generated between the collector-emitter. FIG. 3 is a characteristic diagram showing the relationship between leakage current Ice. 1.2.3...Transistor, 4...
Input terminal, 5... Output terminal, 6... Power supply terminal, 7... Diode.

Claims (1)

[Claims] 1. A transistor circuit comprising two or more transistors connected in a Darlington connection, and a voltage dropping element or circuit element connected between the collector of at least an input stage transistor of the transistor group and a power supply or a reference voltage source.