| 摘要 |
<p>PURPOSE:To lower the output voltage especially at the time of the low level for the schmitt circuit featuring the emitters connected in common, by obtaining the output from the emitter resistance circuit. CONSTITUTION:When the input voltage features a low level less than the sum value of the common emitter voltage and threshold level VBEQ1, transistor Q1 is off with Q2 turned on. And the output voltage features almost R4/(R1 R2+R3+R4). VCC. When the input voltage exceeds the sum of the emitter voltage and VBEQ1, Q1 is turned on with Q2 turned off. If R1>R2 is secured, a positive feedback loop is secured between the current increment due to the ON of Q1 and the current decrement due to the OFF of Q2. Thus the output voltage under the steady state features as R4/(R1+R3+R4).VCC. In this case, the relation of R4/(R1 +R2+ R3+R4).VCC>VBEQ3>R4/(R1+R3+R4).VCC is secured between the output voltage and threshold level VBEQ3 of driving transistor Q3. As a result, the driving transistor can be driven directly by the output given from the emitter side.</p> |
