EECS 100B, Midterm #1, Spring 1982
EECS 100B, Spring 1982
Midterm #1
Professor J.M. Smith
Problem #1
An n-type silicon wafer has 1015 phosphorous atoms per cubic centimeter. Boron is diffused into the crystal
with the surface concentration of C0=1019 per cubic centimeter. The diffusion constant D is 8 cm2 per
second. The time of diffusion is only 3.125x10-10 seconds. The resulting distance constant L is 10-6 meters.
What is the concentration of p-type boron at the depth of 2.5 micrometers?
Problem #2
A DTL NAND gate has all inputs tied together at 5 volts. The resistor to the power supply of 5 volts from the
input diode anodes is 5000 ohms, the collector resistor is 2000 ohms. The load capcitance from the collector
to ground CL is 50 picofarads (50x10-12). The capacitance from the input diode anodes to ground CD is 10
picofarads.
(a) Assuming CD is negligible, what is the time constant of the output circuit when the signals to all input
diodes go to zero simultaneously and instantly?
(b) Assuming CL is neglible and all inputs are zero volts, what is the time constant of the voltage at the diode
anodes when the signals to all input diodes go to 5 volts simultaneously and instantly?
Problem #3
Draw the circuit for a TTL NAND gate with push-pull output circuit. Show at least two inputs.
Problem #4
Construct the truth table for
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