JPS6198015A - Source voltage clamping circuit - Google Patents

Abstract

PURPOSE:To impress a voltage lower than a specific voltage to the active element in a circuit by connecting the emitter of a bipolar transistor (TR), whose collector potential and base potential are fixed respectively to the active element. CONSTITUTION:The collector of the bipolar TRQ1 is grounded and the base is connected to a constant voltage circuit 31, so the collector potential and emitter potential are fixed. When a negative-side source voltage Vcc is not so high (V1<V2+VD1+VD2), the TRQ1 is off and the voltage clamping circuit 3 does not operate, so that V1 varies following up a negative-side source voltage VEE together with a reference voltage VCS. When the negative-side source voltage VEE rises, TRQ1 turns on and the voltage V1 is clamped and limited to below V2+VD1+VD2, where VD1 and VD2 are forward voltage drops across diodes D1 and D2.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a power supply voltage clamp circuit, for example, in a highly miniaturized semiconductor integrated circuit device, the voltage applied from the power supply to the active elements in the circuit is This relates to an effective technique that can be used to limit the breakdown voltage of an element so as not to exceed it.

[Background technology]

For example, as described in the Nikkei Electronics magazine published by Nikkei McGraw-Hill on November 22, 1982, on pages 179 to 194, the miniaturization of bipolar ICs (semiconductor integrated circuit devices), as well as MO5 ICs, is It's progressing.

By the way, as ICs become more miniaturized, their breakdown voltages decrease due to the reduction in the dimensions of individual elements. This makes it difficult to maintain the current ratings.

For example, FIG. 2(a) shows a current switch circuit commonly used in industrial IJ near ICs, interface ICs, and the like. In addition, FIG. 6(b) shows the operating characteristics of a portion thereof.

The current switch circuit 1 shown in FIG.
, Qc and resistors Ra, Rh, Re, etc., and operates between the positive power supply VCC and the negative power supply VEE. Then, the difference between the two inputs inA and inB is amplified and output.

Here, the collectors of transistors Qa and Qb are connected to the positive power supply vcc via load resistors Ra and Rb, respectively. Moreover, the transistor Qa.

Each emitter of Qb is connected in common. This common emitter is connected to the negative power supply V via the transistor Qc and the resistor Re. connected to.

The base of the transistor Qc is supplied with a reference voltage ■ from the reference voltage generating circuit 2. S is given. This reference voltage V. 8
is generated so as to maintain a substantially constant potential difference with respect to the negative power supply VIE, as shown in Φ) in the figure. As a result, a constant current determined by the reference voltage VCS and the resistor Re flows through the transistor Qc. In other words, the transistor Qc and the resistor Re form a constant current circuit.

By the way, when the circuit 1 shown in FIG. 2 is formed in a high-density semiconductor integrated circuit device microfabricated to have a minimum dimension of 3 μm or less, each transistor Qa, Qb, Qc
The breakdown voltage between the collector and emitter of the transistor is only about 7V. If a conventional rating is applied to the circuit 1 using a transistor with a low breakdown voltage, the problem arises that the breakdown voltage of the transistor will be exceeded even within the range of the rating. It was clarified by the present inventor.

Incidentally, in the circuit 1 of FIG. 2(a), it is assumed that the maximum ratings are v, .=+';zv, v, .

Then, a maximum voltage of 110.8V (Qa.

Each base-emitter voltage VBE of Qb is set to 0.
．． A voltage of approximately 8V (calculated as 8V) is applied.

Regarding the transistor Qc, as shown in Φ) in the same figure, the voltage v1 at its emitter is the reference voltage V1.
Because it changes along with C8 to follow the negative power supply VE[,
A voltage of about 9V is also applied between the collector and emitter.

Therefore, the breakdown voltage of transistors Qa, Qb, and Qc is 7
．． If it is about 0 V, a problem arises in that it cannot withstand the maximum rating mentioned above.

[Purpose of the invention]

An object of the present invention is to reliably limit the voltage applied from a power supply to an active element in a circuit within the withstand voltage range of the element, with a relatively simple configuration, for example, in a microfabricated semiconductor integrated circuit device. The present invention provides a power supply voltage clamp circuit technology that allows the circuit to have a large maximum rating.

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 overview of typical inventions disclosed in this application is as follows.

In other words, by connecting the emitter of a bipolar transistor (with its collector potential and base potential fixed respectively) to an active element in the circuit, the voltage applied to the active element is limited to a predetermined voltage or less. This achieves the purpose of allowing large maximum ratings.

〔Example〕

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 1(a) shows an embodiment of a power supply voltage clamp circuit according to the present invention. In addition, FIG. 6(b) shows the operating characteristics of the main part.

The power supply voltage clamp circuit 3 shown in FIG. 3A is formed within a highly microfabricated semiconductor integrated circuit device, and is applied from a power source to active elements within a circuit 1 formed simultaneously within the device. The voltage v1 is limited to a predetermined voltage or less. 5, which allows circuit 1 to have a large maximum rating.

First, a circuit 1 to which the power supply voltage clamp circuit 3 is applied
I will explain about it.

This circuit 1 is a current switch circuit that is used in, for example, industrial IJ near ICs and interface ICs. This current switch circuit 1 forms the input circuit of a differential amplifier circuit. , bipolar transistors Qa, Qb, Qc as active elements, and passive elements such as certain resistors Ra, Rb, Re, etc., and operate between the positive side power supply VCC and the negative side power supply V.

Then, the difference between the two inA and inB is amplified and output.

Here, the collectors of transistors Qa and Qb are connected to the positive power supply VCC via load resistors Ra and Rb, respectively. Furthermore, the emitters of transistors Qa+Qb are commonly connected. This common emitter is connected to the negative power supply (■) via the transistor Qc and the resistor Re.

A reference voltage V from the reference voltage generation circuit 2 is applied to the base of the transistor Qc. 8 is given. This reference voltage VC8
is generated so as to maintain a substantially constant potential difference with respect to the negative power supply vEE, as shown in FIG. As a result, transistor Qc has its reference voltage VC8 and resistor R
A constant current defined by e flows. In other words,
Transistor Qc and resistor Re form a constant current circuit.

Next, the power supply voltage clamp circuit 3 will be explained.

　　　.

This power supply voltage clamp circuit 3 consists of a bipolar transistor Q whose collector potential and base potential are each fixed.
It has l. And this bipolar transistor Q1
By connecting the emitter of the circuit 1 to the active element in the circuit 1, that is, the bipolar transistor Qc, the voltage v1 applied to the bipolar transistor Qc from the power supply V
It operates to limit the amount below a predetermined value. In this embodiment, the collector of the bipolar transistor Q1 is connected to ground potential. At the same time, a constant voltage 2 having the same polarity as the applied voltage v1 in the circuit 1 is applied to its base.

To explain the embodiment in more detail, the emitter of the bipolar transistor Q1 is connected to a diode D1.
It is connected to the emitter of the bipolar transistor Qc of the current switch circuit 1 through the forward direction of D2 in series. Further, a constant voltage circuit 31 is provided that applies a constant voltage v2 to the base of this bipolar transistor Q1.

The constant voltage circuit 31 is composed of a bipolar transistor Q2 and resistors R1 and R2. The collector of the bipolar transistor Q2 is connected to the ground potential through the resistor R1 in series.

Further, its emitter is connected to the worker side power supply Vlilil through a resistor R2 in series. Further, the reference voltage VC8 is applied to the base of the bipolar transistor Q2.

As a result, a constant current determined by the reference voltage VC8 and the resistor R2 flows through the bipolar transistor Q2. This constant current flows from ground potential through resistor R1. Therefore, a constant voltage v2 with a fixed potential difference with respect to the ground potential is generated across the resistor R1. This constant voltage 2 is applied to the base of the bipolar transistor Q1.

Next, the operation will be explained.

First, if the voltage of the negative side power supply VCC is not so high,
That is, the voltage v1 at the emitter of transistor Qc
If the value of is smaller than the sum of the voltage (2) at the base of the transistor Q1, the voltage drop between the base and emitter of the transistor Q1, and the forward voltage drop of the diode D1゜D2, the transistor Q1 is turned off.
(non-conducting) state is maintained. In this state, the voltage clamp circuit 3 does not operate. Therefore, the voltage 1 at the emitter of the transistor Qc changes along with the reference voltage VC8, following the voltage of the negative power supply VEE, as partially shown in FIG. 1(b).

On the other hand, the voltage on the negative side power supply V increases, and the value of the voltage (1) at the emitter of the transistor Qc increases to the voltage (2) at the base of the transistor Q1 plus the voltage drop between the base and emitter of the transistor Q1 and the diode DI. ,
When the voltage becomes larger than the sum of the forward voltage drop of D2, the transistor Q1 becomes conductive. As a result, the voltage 1 at the emitter of the transistor Qc is clamped, as shown in FIG. 1(b). As a result, the voltage v1 applied from the power supply VIE to the emitter of transistor Qc is equal to the voltage v1 at the base of transistor Q1.
2 plus the voltage drop between the base and emitter of the transistor Q1 and the forward voltage drop of the diodes DI and D2. The clamp value can be arbitrarily set by the respective values of the resistors R1 and R2 or the number of series connections of the diodes DI and D2.

In the manner described above, it is possible to prevent the voltage applied between the collector and emitter of the transistor Qc from exceeding its breakdown voltage. Along with this, transistors Qa, Q
The voltages applied between the respective collectors and emitters of b can also be limited to below a predetermined value. This allows the circuit 1 while allowing a large maximum rating externally.
The voltages applied between the collectors and emitters of the transistors Qa, Qb, and Qc within the circuit can be reliably kept within the range of their withstand voltages (approximately 7 cm).

〔effect〕

(1) By connecting the emitter of a bipolar transistor whose collector potential and base potential are each fixed to an active element in the circuit, the voltage applied from the power supply to the active element can be limited to a predetermined voltage or less. ,
This has the effect of allowing the circuit to have a large maximum rating.

Although the invention made by the present inventor has been specifically explained above based on examples, it goes without saying that this invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Nor. For example, the constant voltage circuit 31 may be configured using a constant voltage element such as a diode. Further, the power supply voltage clamp circuit 3 can be shared by a plurality of circuits.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to a high-density bipolar type semiconductor integrated circuit device, which is the background field of application, but the invention is not limited thereto. Bi-MO8 element and MO8 element are mixedly formed.
It can also be applied to type semiconductor integrated circuit devices. It can be applied at least to conditions where it is necessary to limit the applied voltage within the circuit to a predetermined value or less.

FIG. 3 is a diagram illustrating an example along with operating characteristics of a part thereof.

1... Circuit, 2... Reference voltage VC8 generation circuit, 3
...Power supply voltage clamp circuit, 31... Constant voltage circuit,
vcc l VEE”・Power supply, Q a , Q b t
Qc - Q1 + Q2... Bipolar transistor, Ra, Rb, Rc.

R1, R2...Resistance, ■1... Voltage applied to the circuit 1 (voltage at the emitter of transistor Qc), ■2
...Constant voltage.

Claims (1)

[Claims] 1. A power supply voltage clamp circuit that limits the voltage applied from a power supply to an active element in a circuit to below the withstand voltage of the active element, which is a bipolar circuit in which the collector potential and base potential are fixed respectively. A power supply voltage clamp circuit characterized in that the emitter of a transistor is connected to an active element in the circuit. 2. The bipolar transistor according to claim 1, wherein the collector of the bipolar transistor is connected to a ground potential, and a constant voltage having the same polarity as the voltage applied in the circuit is applied to the base of the bipolar transistor. Power supply voltage clamp circuit.