JPS63180214A - Electronic circuit - Google Patents

Abstract

PURPOSE:To output an H level without losing the performance of dielectric strength by connecting a gate of an N-channel transistor (TR) to an input of a NOT circuit. CONSTITUTION:In case of the presence of pull-up option P-O, a depletion TR is used for N-channel TRs NTR 7, 8 and an input of a NOT circuit 10 goes to an H level and the output goes to an L level. An L level is fed to the gate of a pull-up TR PTR 6, which is turned on and an input of the circuit 10 is applied to the gate of the NTR 7, and since the depletion TR is employed, the resistance between the power supply 1 and the output terminal 3 is small and the pull-up state outputting the H level is attained. In the absence of P-O, a depletion TR is given and the input of the circuit 10 goes to an L level and the output goes to an H level. An H level is fed to the gate of the PTR 6, which is turned off. An enhancement TR is used for the NTR 7, an input of the circuit 10 is fed to the gate, which is turned off and the power supply 1 and the terminal 3 are disconnected. Thus, the H level is outputted without losing the performance of dielectric strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electronic circuits such as microcomputers, and particularly relates to improvements in pull-up option circuits thereof.

[Conventional technology]

A conventional pull-up option circuit of this type is shown in FIG. In the figure, 1 is a power supply, 2 is a ground, 3 is an output terminal, and 4 is an N-channel transistor for the output sofa.

In addition, a pull-up option circuit is configured from 5 to 10, and 5 is a depletion mask, which is used to change a desired one of the N-channel transistors 7 to 9 for pull-up selection into a depletion type transistor. 6 is a P-channel transistor for pull-up, and 10 is a negative circuit.

Next, the operation will be explained. First, consider the case with a pull-up option. At this time, the N-channel transistors (pull-up selection transistors) 7 and 8 are made into a depression type by applying depression.

As a result, the input of the NOT circuit 10 becomes H (high) level, and the output of the NOT circuit 10 becomes L (low) level. By doing so, an L level is applied to the gate of the pull-up P-channel transistor 6, and the transistor 6 is turned on. Since an L level is applied to the gate of N-channel transistor 7, it is normally in an on state, and power supply 1 and output terminal 3 are connected to transistor 6.7.
It is in a state where it is connected through a resistor, that is, it is in a pull-up state.

Next, consider the case without the pull-up option.

At this time, the N-channel transistor 9 is made into a depletion type by applying a depletion voltage. As a result, the input of the NOT circuit 10 goes to the L level, and the output of the NOT circuit 10 goes to the H level. By doing so, an H level is applied to the gate of the pull-up P-channel transistor 6, and the transistor 6 is turned off. Since the N-channel transistor 7 is not depleted, it is of the enhancement type, and since the L level is applied to its gate, it is in the off state, and the power supply 1 and the output terminal 3 are disconnected. .

The role of the N-channel transistor 7 here is to increase the breakdown voltage. Assuming that there is no N-channel transistor 7, even if the P-channel transistor 6 is off, the power supply 1 and the output terminal 3 are connected through the diode of the transistor 6, and a voltage higher than the power supply 1 is applied to the output terminal 3. Then, current flows from terminal 3 to power supply 1.

Therefore, by providing the N-channel transistor 7,
The withstand voltage can be increased up to the breakdown voltage of the transistor 7.

[Problem that the invention seeks to solve]

As mentioned above, the gate of the N-channel transistor 7 in the conventional pull-up option circuit is at the L level regardless of the presence or absence of the pull-up option, so unless the transistor size is increased and the resistance value is decreased, the output will be reduced. There are problems in that it is difficult to output an H level to the terminal 3, and the output H level is affected by variations in the resistance value of the transistor 7.

The present invention has been made to solve the above-mentioned problems, and aims to provide an electronic circuit that can reduce transistor size without impairing voltage resistance performance and that can easily output an H level.

[Means for solving problems]

In the electronic circuit according to the present invention, the gate of the N-channel transistor 7 of the conventional circuit is connected to the input of the negative circuit 10.

[Effect]

In the electronic circuit of the present invention, by connecting the gate of the N-channel transistor 7 of the conventional circuit to the input of the inverting circuit 1o, the voltage applied to the gate of the transistor 7 is made variable depending on whether pull-up is performed or not. If there is a pull-up, an H level is applied to the gate of the transistor 7, which makes it easier to output an H level to the output terminal 3, and if there is no pull-up, an L level is applied to the gate of the transistor 7. Even if the transistor size is reduced, the same breakdown voltage as before can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an electronic circuit according to an embodiment of the present invention. In the figure, the configurations 1 to 10 are almost the same as the conventional one, and conventionally the gate input of the N-channel transistor 7 is connected to ground. In this embodiment, it is connected to the input of the inverter 10, that is, to the commonly connected main electrodes of the two pull-up selection transistors 7.8.

Next, the operation will be explained. First, consider the case with a pull-up option. At this time, by applying depression to the N-channel transistor 7.8, the input of the NOT circuit 10 becomes H (high) level, and the input of the NOT circuit 10 becomes H (high) level.
The output becomes L (low) level. When an L level is applied to the gate of the pull-up P-channel transistor 6, the transistor 6 is turned on. The gate of the N-channel transistor 7 has a negative circuit 100 input, that is, an H
Since the level is added and the transistor is of a depletion type, the resistance value of the N-channel transistor 7 is extremely small4. Therefore, the resistance value between the power supply 1 and the output terminal 3 is small, resulting in a pull-up state in which a steady H level is output.

Next, consider the case without the pull-up option.

At this time, the N-channel transistor 9 is made into a depletion type by applying a depletion voltage.

As a result, the human power of the NOT circuit 10 goes to the L level, and the output of the NOT circuit 10 goes to the H level.

H to the gate of pull-up P channel transistor 6
By adding the level, the P-channel transistor 6
is turned off. Since the N-channel transistor 7 is not depleted, it is of the enhancement type, and the input of the inverter 10, that is, the L level, is applied to the gate, so it is in the off state, and the power supply 1 and the output terminal 3 are disconnected. become separated. In other words, the state is the same as that of the conventional one, and the breakdown voltage can be improved up to the breakdown voltage of the transistor 7.

In the above embodiment, the case of a pull-up option circuit was explained, but by increasing the size of the P-channel transistor 6, the form of the output port can be made optional, that is, an N-channel open drain type, or a CMOS output It can also be changed to an optional circuit for selecting the type, and the same effect as the above embodiment can be achieved.

〔Effect of the invention〕

As described above, according to the electronic circuit according to the present invention, by only slightly modifying the existing pull-up option circuit, it is possible to obtain a compact circuit that is easy to output "H" level without impairing voltage resistance performance. be.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a pull-up option circuit of an electronic circuit according to an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional pull-up option circuit. In the figure, 1 is the power supply, 2 is the ground, 3 is the output terminal,
6 is a pull-up transistor, 7 is a MOS transistor, 8.9 is a pull-up selection transistor, and 10 is a negative circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (5)

[Claims] (1) It is characterized by comprising a pull-up transistor for pulling up the output terminal and a MOS transistor for separating the transistor and the output terminal, and the voltage applied to the gate of the MOS transistor is variable. electronic circuit. (2) The gate of the above-mentioned pull-up transistor is connected in series between the power supply and the ground, and the gates of the two pull-up selection transistors are connected to the ground. 2. The electronic circuit according to claim 1, wherein the electronic circuit is connected through the electronic circuit. (3) The gate of the MOS transistor is connected to the main voltage that is commonly connected to the input of the inverting circuit and the two pull-up selection transistors. The electronic circuit according to item 2. (4) The above pull-up transistor is a P-channel MO
4. The electronic circuit according to claim 1, wherein the transistor is an S transistor, and the two pull-up selection transistors and the MOS transistor are N-channel MOS transistors. (5) When there is a pull-up option, the one on the power supply side of the two pull-up selection transistors and the above-mentioned MOS transistor are in the depletion type, and when there is no pull-up option, the two pull-up selection transistors are 5. The electronic circuit according to claim 1, wherein one of the circuits on the ground side is of a depression type.