Semiconductor Devices

Paper details:
2 questions from a 5 question physics coursework

El 2_Assignment_2014-2013 X + – X
2: :3 O :33 :l’ : {‘Tew 2533129: * :- 63
5. Using a summing operational amplifier: design a 3-bit digital to analogue converter
(DAC). Assume the digital inputs are generated fiom a TTL circuit (logic 0 equal to O V,
logic 1 equal to 5 V). The converter output should feed a speaker which has a maximum
input voltage of 3.5 V. Draw a diagram of your completed circuit design and explain its
operation-
[10 marks]
1:14 AM
E [D] a Q % “I a A (1″ ’42 E % 25-Aug-15

E 2_Assignment_2014-2013 X
2: :Iiv O Se; ‘ :l” :‘ {WEI e: 3:19;: if :- 6:3
3. Calculate the base current entering each transistor: 131 and 132, and the total current gain,
Btml, for the following circuit (assume that each transistor is made from silicon and has a
V35 of 0.7 V).
[10 marks]
-10 V
131 I
+5 v
V. f = 5°
-‘
132
I R}, = 100 Q