ECEN 231 Solid state devices and Circuits
a) The terminal voltages of various npn transistors are measured during operation in their
respective circuits with the following results:
For each case, identify the mode of operation of the transistor.
b) Determine the current ID and the diode voltage Vn for the circuit in Fig with VDD = 5 V and R
= 1 kΩ. Assume that the diode has a current of 1 mA at a voltage of 0.7 V.
Use the diode equation to estimate for VD for calculated current.
c) An npn transistor having IS = 10−15A and β = 100 is connected as follows: The emitter is
grounded, the base is fed with a constant-current source supplying a dc current of 10 μA, and
the collector is connected to a 5-V dc supply via a resistance RC of 3 kΩ. Assuming that the
transistor is operating in the active mode, find VBE and VCE, then use these values to verify
active-mode operation
d) Design the circuit in Fig to provide an output voltage of 2.4 V. Assume that the diodes
available have 0.7-V drop at 1 mA.
Case
E
B
C
Mode
1
0
0.7
2.7
2
0.1
0.9
0.1
3
-0.7
0
1.0
4
-0.7
0
-0.6
5
1.3
2.0
5.0
6
0
0
5.0
