Question

# 3. a) Explain what is meant by the term 'small signal equivalent circuit'. How is it usedin electronics design? You are required to design a common emitter voltage amplifier (find

values for the resistors) to meet the following specification and criteria: a collector current of Ic 0.75mA, DC voltage rail, Vcc= 15 V and VSE(on) = 0.6 V. b) Sketch the schematic circuit and calculate the four resistor values, Rc. RE, RBI andR32 to meet the required specification, according to the following guidelines: i)Allow 10% of Vcc across RE. ii)about 0.5 Vcc at the collector node, iii)the current in the base bias resistors should be ten times greater than theDC base current, where the DC current gain is 130. Comment on each guideline. c) The voltage gain of your amplifier is required to be greater than G (Given on Cover Sheet). Write down an expression for the voltage gain and hence find the minimum value of load resistor, R_ that could be used, to satisfy this requirement.

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