JPS61237509A - Schmitt trigger circuit - Google Patents

Abstract

PURPOSE:To vary digitally a threshold value by connecting >=2 sets of same channel control MOSes in parallel with each MOS of an inverter comprising series connection of P and N-channel MOSFETs (MOS). CONSTITUTION:Plural P-channel MOSes 8 are connected in parallel with a P-channel MOS 7 and N-channel MOSes 12 are connected similarly in parallel with N-channel MOS 11. An output signal at an output terminal 3 is given to a control input terminal 5 of a gate control circuit 6 to be inputted to a MOS selected out of P and N-channel MOSes 8 and 12 so as to control its conduction. The MOSes not selected are always in cut-off state. The number of transistors conducted or cut off in the MOSes 8, 12 connected in parallel is controlled depending on the number of high level signals inputted to the control input terminal 5. The threshold voltage of this circuit is controlled by the number.

Description

[Detailed description of the invention] [Industrial application field] FIELD OF THE INVENTION The present invention relates to a sinimit trigger circuit.

[Conventional technology]

Conventional phase-1llIi! ! ! A Schmitt trigger circuit using 1 MO8 transistor has two P-channel f
iM08 is connected in series between a field effect transistor and two N-channel type M0811 field effect transistors, and an input signal is commonly applied to the gate electrode of each MO811 field effect transistor, and an intermediate connection point of the series connected MO8 field effect transistors is connected in series. At the same time, this output signal is used to generate two P-channel type M08@ field effect transistors and two N-channel type MUM1! -1 of the field effect transistor, respectively, and fcM
The O8II field effect transistor was turned on or off to increase the threshold voltage 'kf of the entire circuit for the input signal.

[Problem that the invention seeks to solve]

In such a conventional Schmitt trigger circuit, the trigger chamber pressure, that is, the upper and lower threshold voltages are determined by the circuit, and when integrated into an integrated circuit, the trigger voltage t cannot be changed. This method.

If the trigger voltage of the Schmitt trigger circuit is not suitable for the system using the Schmitt trigger circuit, the Schmitt circuit itself has to be redesigned (t1).

[Question A? Means to solve]

The Schmitt trigger circuit of the present invention has positive and negative !
# Each of a plurality of P channels and N channels M between
The sources of the OS transistors are connected in series, the gates of the M08 transistors connected in series are commonly connected to the input terminal, and two or more transistors are connected in parallel to at least one of the transistors in the P-channel channel. The control M(Jl) transistors of the same channel type are connected, and the four control MO8 transistors are controlled by the output signal obtained from the intermediate connection point of the series connection.

〔Example〕

Next, see the entire screen and see the invention? explain.

FIG. 1 shows an embodiment of the present invention.
The input terminal 3 of the trigger circuit is an output terminal. Positive'
FJ! #, 2 between m child 2 and negative tgp, terminal 4
one P channel MO8) Langistav, 9 and two N
Channel transistors 10.11 are connected in series. A plurality of P-channel MOS transistors are connected in parallel to the P-channel MOS transistor 7,
Similarly, a plurality of N-channel MO8) transistors 12 are connected in parallel to the N-channel MO8) transistor 11.

Series connected transistors 7.9, 10. ]The output from the intermediate connection point 1 is sent to the output terminal 3 through the inverter 13.
The output signal from the output terminal 3 is inputted to a selected one of the P-channel MOS transistor 8 and the H-channel MOS transistor 12 by the control input terminal 5 of the gate control circuit 6 to control the conduction thereof. Items that are not selected are always in a blocked state.

In this embodiment, MO8 transistors 8 are connected in parallel to the number of high-level signals input to the control input terminal 5.
．． And it becomes possible to control the number of transistors to conduct or cut off the 12 transistors. By this number, the threshold voltage of the Schmitt trigger circuit can be controlled, and the Schmitt voltage width can be controlled. Specifically, the quamit voltage range of IC can be widened by increasing the number of transistors that are turned on or off depending on the output signal.

〔Effect of the invention〕

As explained above, according to the present invention, the Schmitt trigger voltage can be arbitrarily varied completely digitally.
Trigger circuit can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. l...input terminal, 2...power supply terminal, 3...output terminal, 4...negative power supply terminal, 5...control signal input terminal,
6...Gate control circuit, 7,8.9...P channel MOS transistor, 10,11.12...N channel MOS transistor, 13...Inverter circuit agent ′;:'t+
゛・, Kudzu 1

Claims (1)

[Claims] A plurality of P-channel and N-channel field-effect transistors are each connected in series between power supply terminals, an input signal is commonly applied to the gate of each field-effect transistor, and a signal obtained from the intermediate connection point of these series-connected field-effect transistors. A plurality of control transistors are provided in parallel to predetermined ones of each of the P-channel and N-channel field effect transistors, and a signal obtained from the intermediate connection point is output from the plurality of control transistors. A Schmitt trigger circuit characterized by the addition of selected ones of the input electrodes to the input electrodes.