Hi...
Our teacher asked us to simulate the right side of a circuit that is a NAND port. That right side of the circuit is attached.
I'm trying to prove with LTSpice that the attached circuit (which is part of a circuit that is supposed to work like a NAND port), knowing that Logic Level 0 is Vce between 0V and 1V and Logic Level 1 is Vce between 4V and 5V, needs to have such a Vbb that makes the transistor work within those limits for Level 0 and Level 1.
So, using the net equations for output and input, I have calculated Ic, then Ib and lastly Vbb for Logic Level 0 and Logic Level 1.
For Logic Level 1 I found Ic=455μA, Ib=2.27μA and Vbb=0.927V
For Logic Level 0 I found Ic=1.83mA, Ib=9.8μA and Vbb=1.61V
But if I try these values for Vbb in LTSpice, the Vbb=0.927V looks like OK because Vce < 1V which is OK for Logic Level 0, but for Vbb=1.61V I should get Vce>4V but LTSpice is outputing a value under 3.8V.
Is there anything wrong with my calcs or can it be due to Vbe of LTSpice to be lower than 0.7V???
Our teacher asked us to simulate the right side of a circuit that is a NAND port. That right side of the circuit is attached.
I'm trying to prove with LTSpice that the attached circuit (which is part of a circuit that is supposed to work like a NAND port), knowing that Logic Level 0 is Vce between 0V and 1V and Logic Level 1 is Vce between 4V and 5V, needs to have such a Vbb that makes the transistor work within those limits for Level 0 and Level 1.
So, using the net equations for output and input, I have calculated Ic, then Ib and lastly Vbb for Logic Level 0 and Logic Level 1.
For Logic Level 1 I found Ic=455μA, Ib=2.27μA and Vbb=0.927V
For Logic Level 0 I found Ic=1.83mA, Ib=9.8μA and Vbb=1.61V
But if I try these values for Vbb in LTSpice, the Vbb=0.927V looks like OK because Vce < 1V which is OK for Logic Level 0, but for Vbb=1.61V I should get Vce>4V but LTSpice is outputing a value under 3.8V.
Is there anything wrong with my calcs or can it be due to Vbe of LTSpice to be lower than 0.7V???
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