JPH0537348A - Output circuit - Google Patents

Abstract

PURPOSE:To improve the output responsiveness by connecting an emitter or a collector of a discharge transistor to a base of an output transistor, and connecting the base directly or through a resistance to become the same potential as an emitter of the output transistor. CONSTITUTION:A circuit for driving a base of an output NPN transistor Q4 of an open collector is constituted of NPN transistorsQ1, Q2 and Q3 and resistor R1, R2. An output of a PNP transistorQ5 discharges accumulated charge of the base of the output transistor therefore, a collector terminal is opened. As for a resistorR4 connected to the transrstorQ5, its effect becomes the largest at the time of '0' OMEGA by a resistance for adjusting a discharge effect. In such a way, by providing an opposite polarity transistor, discharge of a base accumulated charge of the output transistor is quickened, and an output response characteristic can be improved thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output circuit composed of bipolar transistors.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example of an open collector output circuit using a bipolar transistor. In FIG. 3, Q4 is an open collector output NPN transistor, R3 is a load resistor, and NPN transistors Q1,
The output transistor Q is composed of Q2 and Q3 and resistors R1 and R2.
A circuit for driving the base of No. 4 is configured. When the Q1 base potential (input) becomes "H" (high potential), Q4 turns on and the output becomes "L" (low potential). When the Q1 base potential becomes "L", Q4 turns off and the output Operates so as to be "H". That is, the entire inverter circuit is configured.

[0003]

By the way, when Q4 is normally saturated in the ON state and changes from ON to OFF, even if the drive current disappears, the input charge is generated due to the accumulated charge remaining in the base of Q4. There will be some time delay from the change of the output to the change of the output. This time delay becomes more significant as Q4 overdrive increases.

The present invention provides one means for reducing the time delay.

[0005]

In order to solve the above-mentioned problems, the base of the output transistor is connected to the emitter or collector of a transistor having a collector terminal or emitter terminal in an open state and having a polarity opposite to that of the output transistor. The base of the reverse polarity transistor is connected to the same potential as the emitter of the output transistor directly or through a resistor.

Further, the base of the output transistor is connected to the base of a transistor having the same polarity (same type) as the output transistor, the collector terminal or the emitter terminal of which is opened, and the emitter of the output transistor has the same potential as the emitter. The emitter or collector of the same polarity transistor is connected directly or via a resistor.

[0007]

By providing the reverse polarity transistor or the same polarity transistor, discharge of the charge accumulated in the base of the output transistor is promoted. Therefore, the responsiveness is improved.

[0008]

EXAMPLES The present invention will be described in detail below based on examples.

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention described in claim 1. In FIG.

In FIG. 1A, Q4 is an open collector output NPN transistor, R3 is a load resistor, and NPN transistors Q1, Q2, Q3 and a resistor R1, are shown.
A circuit that drives the base of the output transistor Q4 is configured with R2. Q5 is a PNP transistor for discharging the electric charge accumulated in the base of the output transistor Q4, and the collector terminal is open. R4 is a resistor for adjusting the discharge effect, and the effect is greatest when it is 0Ω (direct connection).

FIG. 1 (b) shows a discharge transistor connected with the emitter open, which has the same effect as that of FIG. 1 (a).

FIG. 2 is a circuit configuration diagram of an embodiment of the present invention as set forth in claim 2.

In FIG. 2A, Q4 is an open collector output NPN transistor, R3 is a load resistor, and NPN transistors Q1, Q2, Q3 and a resistor R1, are shown.
A circuit that drives the base of the output transistor Q4 is configured with R2. Q5 is an NPN transistor for discharging the electric charge accumulated in the base of the output transistor Q4, and the collector terminal is open. R4 is a resistor for adjusting the discharge effect, and the effect is greatest when it is 0Ω (direct connection).

FIG. 2B shows the discharge transistor connected with the emitter open, and has the same effect as that of FIG. 2A.

[0015]

As described in detail above, according to the present invention, the output response characteristic can be improved with a simple structure.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of an embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a conventional example.

[Explanation of symbols]

Q1, Q2, Q3 NPN transistor Q4 output NPN transistor Q5 Discharge transistor R1, R2 resistance R3 load resistance R4 Discharge effect adjustment resistor

Claims (2)

[Claims] 1. An output transistor having a collector as an output, a circuit for driving a base of the output transistor, and a base of the output transistor having a collector terminal or an emitter terminal in an open state and having a polarity opposite to that of the output transistor. An output circuit having a transistor for discharging accumulated charge, wherein the emitter or collector of the discharge transistor is connected to the base of the output transistor, and the base is connected to the same potential as the emitter of the output transistor directly or through a resistor. An output circuit comprising: 2. An output transistor having a collector as an output, a circuit for driving a base of the output transistor, and a base accumulation of the output transistor having the same polarity as the output transistor with an open collector or emitter terminal. An output circuit having a charge discharging transistor, wherein the base of the discharging transistor is connected to the base of the output transistor, and the emitter or collector is connected to the same potential as the emitter of the output transistor directly or through a resistor. An output circuit comprising: