JPS59218039A - Monolithic switch circuit - Google Patents

Abstract

PURPOSE:To extend the amplitude of an operating signal by using a transistor (TR) having a structure where the collector is grounded and a signal is applied to the emitter in an AC signal switch circuit. CONSTITUTION:The collector of the N conduction is grounded to the substrate via a terminal 8 in a monolithic switch circuit where the saturated region of the NPN TR is made conductive and the cutoff region is made nonconductive. Further, the emitter is connected to a terminal 7 to which an AC signal is applied and a control signal is supplied via a terminal 4. Since the terminal 7 of the signal side and the substrate are separated completely through the constitution above, the limitation of the amplitude of signal due to a diode existing between the substrate and the collector is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a monolithic switch circuit in a monolithic integrated circuit constructed using a P-N junction split pupil technique on a P-type conductive substrate, and in particular to a monolithic switch circuit in a monolithic integrated circuit constructed using a P-N junction separation pupil technique on a P-type conductive substrate, and in particular to This relates to an AC switch/circuit that uses a conductive region and a non-conductive region.

FIG. 1 shows an example of a switch circuit for explaining the present invention. In order to make it easier to understand the present invention, this will be explained first.

In the figure, (1) is an input terminal to which an AC signal is applied. (2) is the resistor connected to this input terminal (1), (
3) is a capacitor connected to this resistor (2), and these constitute a voltage dividing circuit. (4) is a terminal to which a control signal is applied, (5) is a switch circuit controlled by this control signal, and this switch circuit (5) is connected to the terminal (7) connected to the capacitor (3) and grounded. Terminal (8)
It is inserted between. (6) is an output terminal from which an output signal is obtained.

In the circuit thus tolerated, the AC signal applied to the input terminal (1) opens and closes the switch circuit inserted between the terminals (7) and (8), and the resistance (2 ) and a capacitor (3), the resultant signal is unattenuated or attenuated and obtained at the output terminal (6).

The present invention aims to realize this switch circuit (5) with a simple transistor circuit suitable for a monolithic integrated circuit.

[Prior art]

An example of the connection mode of conventional transistors in this type of switch circuit is shown in FIG. 2 and will be explained. FIG. 2 shows an NPN transistor used as the above-mentioned switch circuit, and FIG. 3 shows how it operates as a switch. For the purpose of explanation, the output characteristics of this transistor are shown.

In Fig. 2, (9) is an NPN) transistor whose collector is connected to the terminal (7) shown in Fig. 1, its emitter is grounded via the terminal (8), and its base is applied with a control signal. Connected to terminal (4). In addition, (1
0) is the collector fll of NPNI-, 7 register (9)
It is a diode with l as the cathode.

In a circuit with such a configuration, when a sufficient base current is supplied to the NPN transistor (9), the collector-emitter current/voltage characteristics are expressed as follows: collector-to-emitter current/voltage characteristics are plotted on the horizontal axis with the collector-pace voltage Vex and on the vertical axis with the collector current Ic. As shown in Fig. 3, it enters the saturation region and thick @ (
As shown in 11), a conductive state is established in which the conductivity is determined by the collector saturation resistance.

Furthermore, when the pace current of the NPN transistor (9) is cut off, it enters the cut-off region and becomes non-conductive, as shown by thick a (12). This conductive/non-conductive state can be used as a switch.

If the NPN transistor (9) shown in FIG. 2 is applied to the switch circuit (5) shown in FIG. Then, NPN ) transistor (
If the saturation resistance value of resistor (9) is made sufficiently smaller than the resistance value of resistor (2) shown in the gt diagram, the signal voltage drop between the collector and emitter of the NPN transistor (9) will be sufficiently small, as shown in Figure 3. The nonlinearity shown by the thick line (11) can be ignored, and the switch can be put to practical use.

However, if the NPN ) transistor (9) shown in FIG. Since the diode (1o) has an anode on the substrate side between the terminal (7) to which the collector is connected and the substrate, and a cathode on the collector side of the NPN transistor (9), the voltage is applied to the collector of the NPN transistor (9). This has the disadvantage that the range of possible voltages is limited. That is, there is a drawback that the voltage amplitude that can be applied to the terminal (.eta.) to which the collector is connected cannot be set to a value that exceeds the forward voltage drop of the diode (10) from the substrate potential.

In order to avoid this drawback of limiting voltage amplitude, it is necessary to apply a lower voltage to the P-type conductive substrate than to the terminal (8) to which the emitter of the NPN I transistor (9) is connected. There is damage. If the NPN transistor (9) is applied as is to the switch circuit (5) shown in Figure 1, the terminal (8) connected to the emitter of the NPN transistor (9) will be connected to the AC signal ground, and the integrated circuit board This means that it is necessary to apply a more negative bias voltage separate from this ground.

[Summary of the invention]

In view of the above points, the present invention has been made to solve such problems and eliminate such drawbacks, and its purpose is to expand the AC signal amplitude applied to the switch circuit without limiting it. Al is committed to providing a monolithic switch circuit that can.

In order to achieve such an object, the present invention connects an N-type conductive collector to the substrate and grounds it, and controls the electrical conductivity between the N-type emitter and the collector by a current flowing into the base. You can use the one you made.

[Embodiments of the invention] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 4 is a configuration diagram showing a connection mode of transistors used in a monolithic switch circuit according to the present invention.

In Fig. 4, the same reference numerals as in Fig. 2 indicate corresponding parts, and (9) is an NPN transistor whose collector is grounded via the terminal (8) and whose emitter is applied with an alternating current signal. It is connected to a terminal (signal terminal) (7) and is configured so that a control signal is supplied to the base via the terminal (4).

In the connection of the transistor configured in this way, as is clear from a comparison with FIG. 2, the terminal (7) on the signal terminal side to which an AC signal is applied is completely separated from the substrate, so The substrate-to-collector diode no longer limits the AC signal amplitude applied to this switch circuit.

Therefore, the AC signal width can be expanded from the forward voltage drop of the diode shown in FIG. 2 (usually about 0.7 V) to the reverse breakdown voltage between the emitter and base of the transistor (usually about 6 V).

FIG. 5 is a circuit diagram showing an embodiment of the monolithic switch circuit according to the present invention, in which the NPN transistor (9) shown in FIG.
This shows a case in which a drive circuit that supplies current to the base of the transistor (9) is also included.

In Fig. 5, the same numbers as in Fig. 4 indicate corresponding parts, (12) is PNP), (14, (
1, 5) are resistors, (16) are NPN) transistors,
(17) is a resistor, and these form a conversion circuit that converts voltage into current, and the conversion gain is set to an appropriate value by the resistor. (18) and (Ig) are resistors, and (20) is a diode, which constitute a voltage dividing circuit. Note that (11) is a current limiting resistor, (1
3) is a power supply terminal, and (21) is a control input terminal to which a control signal is applied.

The collector of the NPN transistor (16) is connected to the power supply terminal (1) through the resistors (15) and (14) in series.
3), its emitter is grounded via a resistor (17), and its base is connected to a control input terminal (21) via a series L resistor (19) and a diode.

The connection point between the base of the NPN transistor (16) and the resistor (19) is grounded via the resistor (18).

Also, the emitter of the PNP ) transistor (12) is connected to the power supply terminal (13), the collector is connected to the base of the NPN ) transistor (9) via the resistor (11), and the base of the PNP ) transistor (12) is connected to the power supply terminal (13). The above resistance (
14) and the connection point of the resistor (15).

Next, the operation of the embodiment shown in FIG. 5 will be explained.

First, when a DC control voltage is applied to the control input terminal (21), the voltage is applied to the diode (20) and the resistor (19).

(18), and the NPN transistor (16) is driven by the divided voltage output and turns on. Here, the operating threshold voltage of the voltage divider circuit L1 drive circuit consisting of this diode (20) and resistors (19) and (18) and the control input voltage applied to the control input terminal (21) are adjusted to an appropriate level. It has the ability to adjust.

Next, when the NPN ) transistor (16) turns on,
The PNP transistor (12) is activated and turns on, and the current is converted through the resistors (14) and (15) and the PNP transistor (12) to drive the NPN transistor (9). transition to the on state.

When no control input voltage is applied to the control input terminal (21), these drive circuits do not operate and the NPN
Transistor (9) is turned off.

In this way, by applying a positive voltage to the control input terminal (21), the NPN transistor (9) can be made conductive, that is, the switch circuit can be closed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a switch circuit for AC signals, when utilizing the saturation region and cutoff region of a transistor, a transistor having a structure in which the collector is grounded and a signal is applied to the emitter is used. Because it uses a A convenient two-way switch that does not require a separate bias power supply and is suitable for monolithic integrated circuits.
;/Since it can be realized with a resistor circuit, the effect of this method is extremely large.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a switch circuit used to explain the present invention;
FIG. 2 is a configuration diagram, not showing a conventional example of how transistors are connected to a switch circuit, FIG. 3 is an explanatory diagram of the switch operation in FIG. 2, and FIG. 4 is a connection state of transistors used in a monolithic switch circuit according to the present invention. FIG. 5 is a circuit diagram showing an embodiment of the present invention. (9)...NPN) transistor, (12)...
・PNP) transistor, (14), (15)...
...Resistor, (16)...-NPN) transistor, (
17) to (19)...Resistor, (20)-...Diode. Agent Masuo Oiwa Figure 1 Figure 3! Figure 4 Figure 5

Claims (1)

[Claims] In a monolithic integrated circuit constructed using a P-N junction separation technique on a P-type conductive substrate, an N-type conductive collector is connected to the substrate and grounded, and a connection is made between the N-type conductive emitter and the collector. A monolithic switch circuit characterized in that the conductivity of fc is controlled by a current flowing into the base.