| 摘要 |
PURPOSE:To obtain easily an invertor provided with a characteristic as an oscillating sub-invertor, by connecting in parallel as auxiliary use a sub-invertor constituted of a short channel transistor, and operating it only when it is necessary. CONSTITUTION:The above figure shows relation of channel length L of a transistor and its threshold voltage VTH, and as a part of ''1'', it is known that when channel length becomes short as <=3mum-4mum, VTH becomes low, and it is generally called a short channel effect of an MOS transistor. Accordingly, when channel length of a transistor for constituting a sub-invertor 3 is set to a value by which the short channel effect appears, an invertor whose VTHP+VTHN is small can be obtained. Channel length of the sub-invertor 3 which applies the short channel effect is about 3mum, and when switches 9, 10 are closed and the sub-invertor is operated, both oscillation start and stop voltages can be dropped by 0.2V or so. |
