JPH0267005A - Analog switch circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an analog switch circuit composed of two-power, two-output bipolar transistors.

BACKGROUND OF THE INVENTION First, the configuration of a conventional one-man-operated, one-output analog switch is shown in FIG. 4 and will be described.

The emitters of the two NPN transistors T1 and I3 are
These two NPN transistors T1, T3 are connected to each other and further connected to the first constant current circuit 1, and have two PNP transistors T4, . An active load consisting of T5 is connected.

These NPN transistors Tl, T3 . Constant current circuit (
1), PNP! - transistor T4. T5 constitutes a differential amplifier circuit. The output of this differential amplifier circuit is NPN
The collector of the transistor T3 is an NPN transistor T.
The collector of this NPN transistor T6 is connected to the DC voltage source Vcc, the emitter is connected to the second constant current circuit 2 and the base of the NPN transistor T3, and the output O of the analog switch circuit is connected to the base of the NPN transistor T3. The input signal I is input from the base of the NPN transistor TI. Furthermore, by providing a switch circuit 5 that connects and disconnects the first constant current circuit 1 and the second constant current circuit 2 according to the switch signal S, the conventional one-manpower, one-output analog switch is configured. .

The equivalent circuit of the above-mentioned one-manpower, one-output analog switch circuit can be expressed as an analog switch 3 as shown in FIG.

Next, when constructing a conventional two-manpower, one-output analog switch, as shown in FIG. 6, two analog switch circuits with one input and one output are used, and their outputs are shared. The output is 0, and the switch signals to the two analog switch circuits are opposite to each other, that is,
The configuration was such that when one side is in a conductive state, the other is in a cut-off state, so that it is applied to one side via the inverter 4.

Problems to be Solved by the Invention ``The configuration of the conventional two-manpower, one-output analog switch described above requires twice the number of elements as the one-manpower, one-output analog switch, which has the disadvantage of increasing the number of elements. Ta.

The present invention aims to solve the above-mentioned problems and provides a two-manpower, one-output analog switch that can be configured with a small number of elements.

Means for Solving the Problems The emitters and collectors of the first and second NPN transistors are each connected in common, and the emitter of the first NPN I-transistor is connected to the emitter of the third NPN transistor, A first constant current circuit is connected to the emitter side of the first NPN transistor, and a first constant current circuit is connected to the emitter side of the first NPN transistor. Third NP
An active load is connected to the collector side of each of the N transistors. Second. A differential amplifier circuit is configured by a third NPN transistor, a first constant current circuit, and an active load, and a third NP transistor that is the output of this differential amplifier circuit is
N) The base of a fourth NPNI transistor is connected to the collector of the transistor, the collector of this fourth NPN transistor is connected to the DC power supply, and the emitter is connected to the second transistor.
is connected to the constant current circuit of the analog switch circuit, and is fed back to the base of the third NPNI transistor through a resistor R3, and is connected to the constant current circuit of the first and second NPN transistors.
The bases of the transistors are connected via resistors R1, R2 having a value equal to this resistor R3 so that the first and second human input signals TI, 12 can be applied thereto, and
The first and second input signals It, 12 are arranged so that when one of them is in a conductive state, the other is in a cutoff state.
It has a configuration in which a switch circuit is connected to the base of an NPN transistor.

Operation When the second NPN transistor T2 is turned off by the switch signal S with the first and second input signals It, 12 being applied, the first NPN transistor T1 is turned off. When the input signal ■1 becomes conductive and, conversely, the first NPN transistor Tl becomes cut off, the second NPN transistor T2 becomes capable of conducting the second input signal ■2. .

Embodiment Hereinafter, an analog switch circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, in which the emitter side of two NPN transistors T1 and T2, whose emitters and collectors are connected in common, is further connected to the emitter side of an NPN transistor T3. NPN transistors Tl, T2 . A differential amplifier circuit is constituted by a constant current source 1 connected to the emitter connection point side of T3 and an active load connected to the collector side.

Here, the active load is two PNP transistors T4
．． T5, both have a common base, both emitters are connected to the DC power supply Vcc, and a PNP transistor T4.
The collector and base of are connected and further connected to the junction of the collectors of the NPN transistors Tl and T2, while the collector of the PNP transistor T5 is connected to the collector of the NPN transistor T3.

NP, which is the output of the differential amplifier circuit configured as described above.
The collector of the NPN transistor T3 is connected to the base of the NPN transistor T6, the collector of this NPNI transistor T6 is connected to the DC power supply Vcc, and the emitter is connected to the constant current circuit 2, and the output of the analog switch circuit is set to 0, and the resistor R3 Through the NPN transistor T3
will be returned to its base.

On the other hand, a resistor R1°R2 having the same value as the resistor R3 is connected to the base of each of the NPN transistors Tl and T2, and input signals It and I2 are inputted through these resistors R1 and R2. Here, resistors R1, R2, R
The reason why the values of 3 are made equal is to equalize the values of offset voltages caused by the base current.

Furthermore, the switch signal S has its emitter at the reference potential 6,
It is input to the base of an NPN transistor T7 whose collector is connected to the base of the NPN transistor T1, and controls the conduction and cutoff of the input signal ■1.
It is input to the base of the transistor T8, and controls whether the input signal I2 is turned on or off via the NPN transistor T9.

Here, the emitter of the NPN transistor T8 is connected to the reference potential 6, and the collector is connected to the NPN I-transistor T.
The emitter of the NPN transistor T9 is connected to the reference potential 6, and the collector is connected to the base of the NPN transistor T2.

The two-manpower, one-output analog switch circuit described above is
This can be expressed by an equivalent circuit of analog switches 3, 3' and inverter 4 as shown in the figure.

In the analog switch circuit according to the embodiment of the present invention configured as described above, the input signal It.

(2) When the switch signal S is input to the NPN transistor T7. When the potential becomes sufficient to make T8 conductive, the collector of NPN transistor T7゜T8 is approximately at the reference potential 6, and the NPN transistor T7
The NPN transistor T1, whose base is connected to the collector of the transistor T1, is cut off. On the other hand, the NPN transistor T9 whose base is connected to the collector of the NPN transistor T8 is also in a cut-off state.
The base is connected to the collector. The NPN transistor T2 becomes conductive to the input signal I2.

Conversely, the switch signal S is connected to the NPN transistor T7.
Since the NPN transistor T7 is in a cutoff state when the voltage that makes T8 conductive is not reached, the NPN transistor TI, whose base is connected to the collector of the NPN transistor T7, allows the input signal 11 to conduct. , the collector of the NPN transistor T8 is approximately at the potential of the DC power supply Vcc, and the collector of the NPN transistor T8 is approximately at the potential of the DC power supply Vcc.
9 is in a conductive state, the collector of this NPN I-transistor T9 is approximately at a reference potential of 6, and the NPN transistor T2 whose base is connected to the collector of the NPN transistor T9 is in a cut-off state. Therefore, due to the switch signal S, only one of the two input signals I1 and 12 becomes conductive, and is output as the output signal O.
A two-manpower, one-output analog switch circuit can be constructed.

To explain the above operation using waveforms, the third
As shown in Figures (a), (b), (c), and (d), when signals with different frequencies are input to the input signals If and I2, and the switch signal S is 0, the lower frequency When the input signal 1 is output as the output signal 0 and the switch signal S is 5, the high frequency input signal I2 is output as the output signal 0.

Effects of the Invention According to the present invention, an analog switch circuit composed of two-manpower, one-output bipolar transistors can be realized with a simple configuration, and the number of circuit elements can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram thereof, FIG. 3 is an operating waveform diagram of an embodiment of the present invention, and FIG. 4 is a conventional one-man operation. (2) A circuit diagram showing an output analog switch circuit, FIG. 5 is an equivalent circuit diagram thereof, and FIG. 6 is a circuit diagram showing a conventional two-manpower, one-output analog switch circuit. 1...First constant current circuit, 2...Second
constant current circuit, 3,3゛...analog switch, 4...inverter, 5,5''...switch circuit, 6...reference potential. Name of agent: Patent attorney Shigetaka Awano Haka 1 person No. 1/71 2t + Circuit diagram

Claims (1)

[Claims] The emitters and collectors of the first and second NPN transistors are connected in common, and the emitter of the first NPN transistor is connected to the emitter of the third NPN transistor, and the emitter of the first NPN transistor is connected to the emitter of the first NPN transistor. is connected to the first constant current circuit, and the first and third NPN
An active load is connected to the collector side of each transistor, and the first, second, and third NPN transistors, the first constant current circuit, and the active load constitute a differential amplifier circuit. The base of a fourth NPN transistor is connected to the collector of the third NPN transistor which is the output of the amplifier circuit, the collector of this fourth NPN transistor is connected to a DC power supply, and the emitter is connected to a second constant current circuit. A resistor R3 is connected to the base of the third NPN transistor to serve as the output of the analog switch circuit.
The first and second input signals I1, R2 are fed back to the bases of the first and second NPN transistors through resistors R1 and R2, each having a value equal to this resistor R3.
The first and second
When one of the input signals I1 and I2 is in a conductive state,
An analog switch circuit comprising a switch circuit connected to the bases of the first and second NPN transistors so that the other is in a cutoff state.