JPH0611012U - Transistor circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a transistor circuit that operates at low voltage and constant current. [Structure] In a circuit using an NPN transistor, the emitter potential is made slightly higher than the collector potential of the NPN transistor, and a constant current control circuit 1 is used.
It is characterized by controlling the discharge current.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a low voltage / constant current circuit, and more particularly to a transistor circuit that utilizes the characteristics of the reverse bias region of an NPN transistor.

[0002]

[Prior art]

 Conventionally, the circuit using the NPN transistor is as shown in Fig. 3, and in order to operate the transistor Q, the collector potential needs to be higher than the emitter potential by 0.6V or more, which results in low voltage and low power consumption. In the circuit used for small electronic devices that require power, use the low saturation region of the PNP transistor to reduce the operating voltage (0.6V) of the transistor, or use the negative voltage to operate on the circuit. It was necessary to take measures such as widening the width.

[0003]

[Problems to be solved by the device]

 However, the circuit using the low saturation region is unstable, and the use of a negative voltage has a drawback that the circuit becomes complicated.

[0004]

[Means for solving the problem]

 The present invention achieves the object by making the emitter potential slightly higher than the collector potential and controlling the base potential in order to eliminate the above problems.

[0005]

【Example】

 FIG. 1 shows an embodiment of a low voltage / constant current circuit using an NPN transistor according to the present invention. A resistor R1 is a current feedback resistor for self bias of Vbc (potential difference between base and collector), and R2 is a circuit. A control voltage detection resistor, Q1 is an NPN transistor, E is a battery, and 1 is a constant current control circuit.

In FIG. 1, Ib (base current) is supplied from the constant current control circuit 1 to the transistor Q1 via the resistor R1 and the emitter of the transistor Q1 is connected to the battery ▲ E to produce a constant current proportional to Ib. It can be taken out from the battery E. That is, ▲, by changing Ib, the current value taken out from the battery E can also be changed. Now, when a 1.2V battery is connected to the emitter of the transistor Q1, a bias voltage as shown in Fig. 2 is obtained, and the operating voltage of the transistor Q1 is 0.2V, so a current of 1A is taken out from the battery. At this time, even if a resistor of 1Ω is used for R2, the voltage drop due to R2 is 0.
4V, the battery voltage is 0. It becomes possible to take out current until the voltage drops to about 7V. ▲ [0007]

[Effect of device]

 As described above, the transistor circuit according to the present invention is a low voltage / constant current circuit that can lower the operation starting voltage of the transistor itself, and can be applied to various circuits. It is especially suitable for the charging circuit of nickel-cadmium batteries that require a constant current.

[Brief description of drawings]

FIG. 1 is a transistor circuit according to the present invention.

FIG. 2 is a diagram showing a relation of a bias voltage of a transistor in the example.

FIG. 3 is a conventional transistor circuit.

[Explanation of symbols]

 1 Constant current control circuit Q, Q1 Transistor E Battery R, R1, R2, Resistance

Claims (1)

[Scope of utility model registration request] A low-voltage / constant-current transistor circuit in which the emitter potential is higher than the collector potential and the base potential is higher than the collector potential in a circuit using NPN transistors.