Schmitt trigger circuit with a hysteresis characteristic.

摘要

Disclosed is a schmitt trigger circuit having an input-voltage hysteresis characteristic for reducing noise sensitivity and preventing oscillation, comprising in its input stage a multi-emitter transistor (T11) and in its output stage a second transistor (T2). The multi-emitter transistor comprises a first emitter (E1) and a second emitter (E2). The first emitter is associated with a switching operation in response to the input voltage (Vin) applied to the base of the multi-emitter transistor. The second emitter is associated with the operation of drawing charges from the base of the second transistor (T2) through the base of the multi-emitter transistor (T11) to the ground. By using the multi-emitter transistor, the input current (I1L) does not greatly increase as the input voltage (Vin) falls.