| 摘要 |
PURPOSE: To prevent a measuring circuit connected with an output terminal, by making the impedance between the input and the output terminals high or low, according to an input voltage. CONSTITUTION: When an input signal is in a desired range, MOSFET's 24, 44 turn on, and the impedance between an input terminal 10 and an output terminal 20 becomes low. When the input signal exceeds a positive desired maximum value, the MOSFET 24 is biased to be in the OFF state, and an input current is limited by a high impedance, thereby eliminating the signal from the output terminal 20. When the input signal exceeds a negative desired maximum value, the MOSFET 44 is, similarly, biased to be in the OFF state. Bipolar transistors 30, 48 increase the changing speed of the MOSFET's to the OFF state. |
