Semiconductor Devices

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