| 摘要 |
<p>PURPOSE:To secure the sufficient operation for P-ROM circuit even with the low power voltage by performing the writing of the information with the short-circuit breakdown to the Zener diode. CONSTITUTION:For writing of the program, the writing current of the proper scale is flowdd to output terminal 6 from input terminal 3, and the short-circuit breakdown is given to Zener diode 2. Now terminal 6 is connected to the power source via the proper load, and the proper input voltage is applied to terminal 3. In this case, transistor Tr1 never conducts as long as the voltage of terminal 3 does not exceed the sum of the breakdown voltage of diode 2 and base-emitter forward voltage VBE of Tr1 and in case no writing is given for the information. Thus terminal 6 is kept at a high level. While in case the writing of the information is given, Tr1 conducts when the voltage of terminal 3 exceeds voltage VBE. And thus terminal 6 draws the output current in. Accordingly, the voltage required for reading of the information will suffice with the level which is a little higher than VBE.</p> |
