| 摘要 |
PURPOSE:To attain stable operation at all times by providing an amplitude limit circuit limiting the amplitude of an input signal to a value below the operating power supply voltage so as to limit its input signal when an excessive input signal is applied. CONSTITUTION:When a signal Vin to be processed is applied to a signal input terminal 1, the operating state of transistors (TR) 10, 11 depends on the relation of amplitude between said Vin and the base voltage of the TR11, that is, a voltage V3 of a DC voltage source 13. When Vin<<V3 at first, the TR10 is turned on and the TR11 is turned off and a voltage V0 produced at a common emitter connecting point of the TRs 10, 11 is expressed as V0=Vin+VEB10, where VEB10 is an emitter-base forward voltage of the TR10 and its value is nearly 0.7V. When Vin<<V3, the TR10 is turned off and the TR11 is turned on, and the voltage V0 in this case is expressed as V0=V3+VEB11, where VEB11 is an emitter-base forward voltage of the TR11 and this value is also nearly 0.7V. |
