JPH02186714A - Analogue switch - Google Patents

Abstract

PURPOSE:To secure a wide input output voltage range and to control the fluctuation of a characteristics due to element fluctuation by permitting an analogue switch to form a full feedback amplifier circuit instead of the differential amplifier of an open loop. CONSTITUTION:The first full feedback amplifier circuit of the analogue switch consists of first and second transistors(Tr) 1, 2 and Tr 7 and resistors 8 and 9. A second full feedback amplifier circuit consists of Tr 3, 4 and Tr 7 and the resistors 8 and 9. Both amplifier circuits are controlled to get into an active state and an interruption state by the action of a differential couple consisting of Tr 5 and 6. The differential couple can be controlled by inputting control voltages from control terminals 22 and 23. Consequently, the input of the full feedback amplifier circuit which is in the active state by the control voltage is outputted to an output terminal 24. Consequently, the gain fluctuation of the feedback circuit can be secured and the wide input output voltage range can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an analog switch, and particularly to an analog switch that stably switches electrical signals in an electronic circuit.

[Conventional technology]

Conventionally, such analog switches are formed by differential amplifier circuits, such as open-loose differential amplifier circuits.

FIG. 2 is a circuit diagram of a conventional analog switch.

As shown in FIG. 2, such an analog switch includes first and second transistors 1, 2 and resistors 8.9 and 1.
3.14, and a second differential amplifier consisting of third and fourth transistors 3.4 and resistors 8.9 and 16.17. . These first and second differential amplifiers are controlled by a differential pair made up of fifth and sixth transistors 5 and 6. That is, the differential pair consisting of transistors 6 is controlled by control input voltages from the first and second control terminals 22 and 23 connected thereto, and the input terminal 20 of the differential amplifier is in an active state or a cutoff state. Alternatively, a signal corresponding to the input signal from 21 is output. In short, the control input voltage from the control terminal 22 or 23 causes the first input terminal 20 or the second input terminal 2 to
This means that the electrical signal has been switched from 1.

Note that the electric currents J12, 15, . 1s is a constant voltage source.

[Problem to be solved by the invention]

The conventional analog switches mentioned above use open-loose differential amplifiers, so the values and characteristics of the elements used directly affect the output voltage, narrowing the input/output voltage range and causing element fluctuations. This has the disadvantage that the fluctuation of the output signal with respect to the input signal becomes large.

An object of the present invention is to provide an analog switch that can secure a wide input/output voltage range and suppress the effects of element fluctuations.

[Means to solve the problem]

The analog switch of the present invention includes a first transistor whose collector is connected to a constant voltage source through a first resistor and whose base is connected to a first input terminal; a second transistor whose collector is connected to the constant voltage source and whose base is connected to the output terminal; and a third transistor whose collector is connected to the collector of the first transistor and whose base is connected to the second input terminal. , a fourth transistor whose collector is connected to the collector of the second transistor and whose base is connected to the output terminal; and a fourth transistor whose collector is connected to the emitters of the first and second transistors and whose base is connected to the first control terminal. a sixth transistor whose collectors are connected to the emitters of the third and fourth transistors and whose bases are connected to the second control terminal; a first constant current source both connected to the emitter of the transistor; and a fourth transistor whose collector is connected to the constant voltage source and whose emitter is connected to the output terminal and whose base is connected to the collector of the fourth transistor. 7 transistors and a second constant current source connected to the output terminal.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

FIG. 1 is a circuit diagram of an analog switch showing an embodiment of the present invention.

As shown in FIG. 1, the analog switch of this embodiment differs from the analog switch of FIG. Another feature is that the output voltage is fed back to the base of the third transistor 3, and that the seventh transistor and the second constant current source 11 are provided to extract the output voltage from the emitter side.

First, the collector of the first transistor 1 is connected to the constant voltage source 12 via the first resistor 8, and the base of the first transistor 1 is connected to the first input terminal 20.

Further, the emitter of the first transistor 1 is connected to the collector of the fifth transistor 5 together with the emitter of the second transistor 2, and the collector of the second transistor 2 is connected to a constant voltage source via a second resistor 9. 12. The base of this second transistor 2 is connected to the output terminal 24 as described above. First Transis evening 1 this 2
and the first resistor 8 are connected to the collector of the third transistor 3, and the connection point between the collector of the second transistor 2 and the second resistor 9 is connected to the collector of the fourth transistor 4 and the third transistor 3. It is connected to the base of the seventh transistor 7. As described above, the emitters of the seventh transistors 1 to 1 are connected to the second constant current source 11, the output terminal 24, and the base of the fourth transistor 4, and the collector of the seventh transistor 7 is connected to the constant voltage source 12. connected to. Further, the base of the third transistor 3 is connected to the second input terminal 21, and its emitter is connected to the collector of the sixth transistor 6 together with the emitter of the fourth transistor 4. On the other hand, the base of the fifth transistor 5 is connected to the first control terminal 22, and its emitter, together with the emitter of the sixth transistor 6, is connected to the first constant current source 10. The base of this sixth transistor 6 is connected to the second control terminal 23.

Next, the circuit operation of the analog switch having such a configuration will be explained.

First, this analog switch includes a first all-feedback amplifier circuit consisting of first and second transistors 1.2, transistor 7 and resistor 8.9, as well as transistor 3.
A second full feedback amplifier circuit composed of a transistor 4, a transistor 7, a resistor 8, and a resistor 9 is controlled into an active state and a cutoff state by the operation of a differential pair composed of a transistor 5 and a transistor 6. Ru. The differential pair constituted by these transistors and the transistor 6 can be controlled by inputting control voltages from the control terminals 22 and 23, as described in the conventional example. Therefore, the input of the full feedback amplifier circuit activated by the control voltage is output to the output terminal 24.

In this way, in this example, two sets of full feedback amplifier circuits are used instead of two sets of differential amplifiers in a conventional analog switch, so that the characteristics of negative feedback circuits are reduced gain fluctuation and wide input/output range. A voltage range can be secured.

〔Effect of the invention〕

As explained above, in the analog switch of the present invention, by forming a full feedback amplifier circuit instead of an open-loose differential amplifier, it is possible to secure a wide input/output voltage range and suppress fluctuations in characteristics due to element fluctuations. There is an effect.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an analog switch showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of an analog switch showing an example of the conventional art. 1-7...transistor, 8.9...! Resistor, 10
11... Constant current source, 12... Constant voltage source, 20.21
...Input terminal, 22.23...Control terminal, 24...
・Output terminal.

Claims (1)

[Claims] a first transistor having a collector connected to a constant voltage source via a first resistor and a base connected to a first input terminal; a collector connected to the constant voltage source via a second resistor; a third transistor whose collector is connected to the collector of the first transistor and whose base is connected to the second input terminal; a fourth transistor whose collector is connected to the output terminal and whose base is connected to the output terminal; and a fifth transistor whose collector is connected to the emitters of the first and second transistors and whose base is connected to the first control terminal. a sixth transistor whose collector is connected to the emitters of the third and fourth transistors and whose base is connected to the second control terminal; the sixth transistor is connected together to the emitters of the fifth and sixth transistors; a seventh transistor having a collector connected to the constant voltage source, an emitter connected to the output terminal, and a base connected to the collector of the fourth transistor; and a second constant current source connected to the terminal.