The BJT circuit shown in Figure 2(a) is a logic NOR gate. This circuit is a member of Resistor-Transistor Logic (RTL) family of logic gates, where we use one or more BJTs and resistors to build the logic gate.
Figure 2(a). RTL NOR gate circuit
Vout [V]
5.0
<0.2 [V]
0.2
0
1.5
4.5 5
Vn[V]
i.5
4.5 5
Vin [V]
Figure 2(b). (Vout vs Vin) for NOR gate when Vin=0 [V]
Figure 2(c). (Vout vs Vin) for NOR gate. (when Vin=5 [V])
1. [Design Parameters] Determine Vcc, R1, R2, and R3 to have Vout vs Vin voltage transfer characteristic as shown in Fig. 2(b) with 0V < Vin < 5V when Vin = 0V and Fig. 2(c) with 0V < Vin < 5V when Vin = 5V. Justify your results. (You can complete this in step (3))
(3) Complete circuit analysis for NOT gate circuit shown in Fig. 1(a).
a. Draw equivalent circuits. Consider BJT junctions (B-E junction, B-C junction, C-E junction). Find corresponding input voltage ranges. (Hint: BJT will operate in Cut-off, Forward Active, and Saturation, depending on the voltage input, Vin)
b. Perform linear circuit analysis for each input voltage range. (Find all current and voltages)
c. Predict (Vout vs Vin) based on your results from your analysis and draw a 2-D graph.
i. Indicate the boundaries on the x-axis (for Vin) and y-axis (for Vout).