JPS61148917A - Switch circuit - Google Patents

Abstract

PURPOSE:To attain ease of circuit integration by using a control circuit to switch conduction/nonconduction of a diode bridge conducted in two-way to eliminate the need for a switch with mechanical structure. CONSTITUTION:When a switch 11 is closed, an output current of a constant current circuit CS1 flows to a GND and transistors (TRs) Q1-Q5 are turned off. Thus, no current flows TRs Q11, Q12 and the diode bridge 3 is nonconductive. Then both ends of a resistor R1 forming the time constant is not short-circuited. When the switch 11 is switched in the opening state, an output current of the constant current circuit CS1 flows the TR Q1 and the TRs Q2-Q5 are turned on. Thus, the bridge circuit 3 is conducted and both ends of the resistor R1 is short-circuited. The conduction/nonconduction of the diode bridge is controlled by one switch in this way and circuit integration is also attained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a switch circuit suitable for use in controlling frequency characteristics, noise reduction, switching on and off of signal transmission, etc. using - switches.

[Background technology]

Today's electronic devices have come to have multiple functions, and their circuit configurations have inevitably become more complex.1 For example, the "tape recorder" (January 25, 1970, 14th edition, published by Nippon Broadcasting Publishing) Association, p168-170, and p17
7 to 179) are provided with a time constant circuit consisting of a resistor and a capacitor, a switch circuit for switching the time constant, etc. in order to perform equalization during recording and playback, and each is used according to the purpose. It has been shown that

On the other hand, one of the technological trends in electronic equipment is the use of electronic interlocking semiconductor integrated circuits, but switches with a mechanical structure cannot be built into integrated circuits, and the production cost is high. In view of the need to reduce wiring, it is better to reduce the number of wires.

The present inventors have conducted various studies on switch circuits from the above-mentioned technical viewpoint, and have developed a switch circuit particularly suitable for semiconductor integrated circuits.

[Purpose of the invention]

An object of the present invention is to provide a bidirectionally conductive diode bridge and a control circuit that controls the conduction of the diode bridge, thereby reducing the need for mechanically structured switches and making it suitable for semiconductor integrated circuits. The purpose of the present invention is to provide a switch circuit.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief summary of the invention disclosed in this application is as follows:
It is as follows.

In other words, by switching a diode bridge that can transmit signals in both directions into conduction and non-conduction using a control circuit, it is possible to reduce the number of switches in the mechanical structure when controlling the time constant and frequency characteristic -1 negative feedback amount in various electronic circuits. This achieves the object of the present invention, which is to implement it as a semiconductor integrated circuit.

[Embodiment 1] Hereinafter, a first embodiment of a switch circuit to which the present invention is applied will be described with reference to FIG. Note that this embodiment shows an example in which a switch circuit is applied to time constant switching of a time constant circuit.

The feature of this embodiment is that the time constant can be varied without changing the capacitance of the capacitor by short-circuiting or opening both ends of the resistor R by a diode bridge.

A1 is an amplifier, for example, an audio signal is input Vi
It is supplied as n. Capacitors c, , C, and resistors R, , R2 constitute time constant circuit 1. Seven signals to be amplified and transmitted are placed on the input side of time constant circuit 1. At this time, switch circuit 2 The time constant changes as follows depending on whether or not it is operating.

First, the time constant when the switch circuit 2 is not operating will be described.

When the switch 11 is in the position shown by the solid line as shown in the figure,
The switch circuit 2 is inactive and the ends of the resistor R1 are not short-circuited, so there is a resistor R, , between the lines 11 and 12.
Since R2 is connected, 1 time constant @ ' t
= lto Cs + (Rs + R2) determined by C2. Note that Ro in the above equation is the internal resistance of the signal Vs. The time constant τ determines the rise time (attack time) of the signal Vs.

On the other hand, when the switch 11 is switched to the open state, the switch circuit 2 is operated to short-circuit both ends of the resistor R1, and the time constant changes to t'=RoC*+R2C2.

Then, the switch circuit 2 changes the time constant τ as described above.
performs the following operations.

That is, the switch 11 is provided outside the semiconductor integrated circuit (hereinafter referred to as IC). When the switch 11 is in the closed state as shown, the output current of the constant current circuit C81 flows to GND, and no bias voltage is supplied to the transistors Q1 to Q=s.

Since the transistors Qz and Qs are in the off state, no current flows through the transistors Q11 and Q12 that constitute the current mirror circuit, and the diode D @ y D 2 HD 3
The diode bridge 3 made up of HD4 also becomes non-conductive. Therefore, both ends of the resistor R1 are not short-circuited, and the time constant τ is determined as described above.

On the other hand, when the switch 11 is switched to the open state as shown by the dotted line, the output current of the constant current circuit C8° flows through the transistor Qs and the resistor R□1, and the bias voltage vb is obtained. Then, by supplying the bias voltage vb, all the transistors Q2 to Qg are turned on, and first, the resistor R22, F' transistor Q12
Current IS flows through v Q 2 + resistor R□2,
+Vcc power supply to resistor R2,.

Transistor 1□, diode bridge 3. A current I2 flows through the transistor Qay resistor R1.

What should be noted here is that A in diode bridge 3
-8 potential difference.

That is, the potential at point A is determined by seven signals.

Then, the potential at point B changes from the potential at point A to diode D-
The forward voltage Vf is increased.

And the voltage decreased by the forward direction of diode D2, i
Then, the potential becomes the same as the potential at point A. Furthermore, diode D
Looking at the 3yD4 side, the potential is lowered by the forward voltage Vf of the diode D3 and raised by the forward voltage Vf of the diode D4, which is the same potential as the potential at point A.

The fact that the potentials between A and 8 are the same means that A and 8 are electrically coupled, and in other words, the resistance Rt
This means that both ends of the circuit are short-circuited. Therefore, the time constant τ1 changes as described above to control the attack time.

Note that the transistor Q4. Q! l can be used for other purposes as a switch to other circuits.

For example, it can be used as a power switch for an amplifier, and it can also be used as a mode changeover switch.

What is important about the structure of the switch circuit 2 is that one switch 11 having a mechanical structure is used.

The present invention can be used not only for controlling the time constant but also for other purposes, and other than the switch 11, other circuit elements can be easily integrated into ICs.

Moreover, in switching the time constant, there is no need to change the capacitance of the capacitor Cs=C, which is difficult to implement in an IC, and in this respect as well, it can be said that the switch circuit is suitable for implementation in an IC.

[Example-2] Next, a second embodiment of the present invention will be described with reference to FIG.

It should be noted that the circuit configuration and circuit operation of the switch circuit 2 are the same as those of the first embodiment, and therefore, duplication of explanation will be avoided.

In this embodiment, the switch circuit 2 is used for time constant control of the product-total circuit □ circuit.

In other words, resistor 3□ and capacitor C11 are integral circuit 2.
1, and the connection and short-circuiting of the resistor R31 are performed by the switch circuit 2. According to this embodiment, when the switch II is switched to the closed state, the integrating circuit 21 is switched to the R
It now has a time constant determined by 3,XC,,
When the switch 11 is switched to the open state, the resistor R3
, is shorted.

〔effect〕

(1) A switch circuit suitable for IC implementation is obtained by configuring the diode bridge to be conductive and non-conductive with a single mechanical switch. The object of the present invention can be achieved.

(2) The direct current control by the switch II allows control of the transmission signal, which is an alternating current component, and does not have any undesirable influence on the transmission signal during control.

(3) Since the resistance value of the resistor constituting the time constant circuit can be easily controlled, the number of capacitors that contribute to high costs and are unsuitable for IC implementation can be reduced.

The invention made by the present inventor has been specifically explained above based on examples, and the present invention is based on the above-mentioned embodiment.

It goes without saying that the invention is not limited to the examples, and that various changes can be made without departing from the gist thereof.

For example, a resistor may be connected in series to the input side of the diode bridge 3, and the input signal may be applied to the diode bridge via this resistor. Since it is connected to a time constant circuit different from the resistor, the time constant can be varied. Note that this circuit configuration may be provided on the output side of the diode bridge.

Further, as shown in FIG. 3, a switch circuit can be similarly made using a pair of diode circuits and a constant current circuit without using a diode bridge. The circuit operation of the circuit shown in FIG. 3 will be briefly explained.

When the switch 11 is closed, the transistor Qz,
Qs, Q4-Qs, Qs are in the off state, no current flows through the diodes Ds, Dz, and the resistor 31 remains unchanged.

On the other hand, when the switch 11 is open, the transistor Q
2 to Q are turned on. However, Ieq5=Ieq@=
2 Ieq3 (Ieqs t IeQs e
Ie (13 are each transistor Qs = Q@-Q
The emitter size of each transistor is determined so that the emitter current of a is 6. If the potential of the input voltage Vin decreases by ΔV i n,
If a current is drawn from the collector of the transistor Q@, then the diode DI will have the following current.

A current of l-1s flows, and as a result, a current of I+Is flows through D2. Therefore, this signal current is R31
The current flows around R31, and no voltage drop occurs across R31. This means that both ends of R3,
- Equivalent to

[Application field]

In the above description, the invention made by the present invention is mainly applied to the time constant control of a time constant circuit, which is its field of application, but it is not limited to this, and for example, it can be used to control the amount of feedback. be able to.

It can also be widely used in linear ICs.

[Brief explanation of drawings]

FIG. 1 shows a circuit diagram showing a first embodiment of a switch circuit to which the present invention is applied, and FIG. 2 shows a circuit diagram showing a second embodiment of the above switch circuit. FIG. 3 shows a third embodiment of the above switch circuit. ■...Time constant circuit, 2...Switch, 3...-diode bridge, 11...Switch, 21...Integrator circuit, Rs "Rs□...Resistance, C*" C1m
...Capacitor, Q, ~Q1□...Transistor,
D1-D4...Diode, vl...Transmission signal. Figure 1

Claims (1)

[Claims] 1. Equipped with a diode circuit capable of bidirectional signal transmission and a control circuit that controls energization to the diode circuit,
A switch circuit characterized in that the control circuit controls signal transmission by switching a diode circuit into conduction and non-conduction.