Touch sensitive electronic switching circuit for electronic wristwatches

• US 4,160,923 A
• Filed: 12/22/1977
• Issued: 07/10/1979
• Est. Priority Date: 02/05/1975
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ohba, Toshihiro, Maeda, Hidetoshi
• Primary Examiner(s): Anagnos, Larry N.
• Application Number:
  US05/863,087
• Time in Patent Office: 565 Days
• Field of Search: 307/116-118, 307/200 B, 307/360, 307/362, 307/363, 307/304, 307/308, 328/1, 328/4, 328/5, 58/23 R, 58/23 A, 58/23 BA, 58/23 D, 58/50 R, 58/50 A, 361/56, 361/58
• US Class Current: 307/116
• CPC Class Codes: G04G 21/08 Touch switches specially adapted for time-pieces
• CPC Class Codes: H03K 17/302 in field-effect transistor switches
• CPC Class Codes: H03K 17/9645 Resistive touch switches

Abstract

In a touch sensitive electronic switching circuit including a C-MOS inverter, for use in electronic wristwatches, a resistor of 1-10 MΩ is connected to the source electrode of the P-channel MOS type field effect transistor included within the C-MOS inverter, whereby the threshold voltage level of the C-MOS inverter is shifted to a low level to enhance the reliability of the touch sensitive electronic switching circuit. In another embodiment, the resistor of 1-10 MΩ is connected to the source electrode of the N-channel MOS type field effect transistor included within the C-MOS inverter, whereby the threshold voltage level of the C-MOS inverter is shifted to a high level to enhance the reliability of the touch sensitive electronic switching circuit.

Claims

1. A touch sensitive electronic switching circuit for electronic wristwatches including a C-MOS inverter having a P-channel MOS field effect transistor and an N-channel field effect transistor, the gates of the respective transistors being coupled together and the drains of said transistors being coupled together, first and second input terminals for said C-MOS inverter across which an operator'"'"'s body completes an electrical circuit to initiate switching of said C-MOS inverter from one state to another, a bias voltage source of a first level coupled to the source electrode of said P-channel transistor, a bias voltage source of a second level coupled to the source electrode of said N-channel transistor, said first level being higher than said second level, a pull-down resistor connecting said second input terminal with said bias voltage source of said second level, means connecting said first input terminal to said bias voltage source of said first level, and means connecting said second input terminal to a common gate terminal of the P and N channels of the C-MOS inverter, the improvement comprising:

resistor means of a high resistive value connected between said bias voltage source of said first level and the source electrode of said P-channel transistor, the ratio of the resistance of said resistor means to the resistance of said pull-down resistor being within a predetermined range.

2. The touch sensitive electronic switching circuit of claim 1 wherein the resistance of said resistor means is in the range of 1-10 MΩ

and the resistance of said pull-down resistor is approximately 20 MΩ

.

3. The touch sensitive electronic switching circuit of claim 1, wherein the touch sensitive electronic switching circuit is incorporated within an integrated circuit constituting a time calculation circuit of the electronic wristwatch.

4. A touch sensitive electronic switching circuit for electronic wristwatches including a C-MOS inverter having a P-channel MOS field effect transistor and an N-channel field effect transistor, the gates of said respective transistors being coupled together and the drains of said transistors being coupled together, first and second input terminals for said C-MOS inverter across which an operator'"'"'s body completes an electrical circuit to initiate switching of said C-MOS inverter from one state to another, a bias voltage source of a first level coupled to the source electrode of said P-channel transistor, a bias voltage source of a second level coupled to the source electrode of said N-channel transistor, said first level being higher than said second level, a pull-down resistor connecting said first input terminal with said bias voltage source of said first level, means connecting said second input terminal to said bias voltage source of said second level, and means connecting said first input terminal to a common gate terminal of the P and N channels of the C-MOS inverter, the improvement comprising:

resistor means of a high resistive value connected between said bias voltage source of said second level and the source electrode of said N-channel transitor, the ratio of the resistance of said resistor means to the resistance of said pull-down resistor being within a predetermined range.

5. The touch sensitive switching circuit of claim 4 wherein the resistance of said resistor means is in the range of 1-10 MΩ

and the resistance of said pull-down resistor is approximately 20 MΩ

.

6. The touch sensitive electronic switching circuit of claim 4, wherein the touch sensitive electronic switching circuit is incorporated within an integrated circuit constituting a time calculation circuit of the electronic wristwatch.