Question

You are required to design a 2-stage voltage amplifier (find values for RE, RC1, RC2) to meet the following criteria: an input resistance of 400 kΩ and an overall voltage gain equal to or greater than 250, with a resistor output load, RL. Use a common-emitter with emitter degradation (RE) stage for the input, followed by a commonemitter amplifier with bias current equal to 0.5 mA. (VCC = 20 V, βo = 200 and the DC levels of the first and second stage outputs need to be set at half the supply voltage. Allow 10% of VCC across RE). Proceed as follows:

a) You are required to design a 2-stage voltage amplifier (find values for RE,Re, Rca) to meet the following criteria: an input resistance of 400 kΩ and an overall voltage gain equal to or greater than 250, with a resistor output load, RL. Use a common- emitter with emitter degradation (RE) stage for the input, followed by a common- emitter amplifier with bias current equal to 0.5 mA. Vcc-20 V, B. 200 and the DC levels of the first and second stage outputs need to be set at half the supply voltage. Allow 10% of Vcc across Re). Proceed as follows: i) Draw a schematic circuit of your amplifier, omitting the bias resistors and coupling caacitors. ii Work out the bias current and emitter resistor value to meet the input resistance specification. Hence find the value of the collector resistor of the first stage. iii) Work out the gain of the first stage and hence find the required gain of the 2nd stage to meet the specification iv) Estimate the minimum value of load resistance, R to satisfy the specification of voltage gain. b) Comment on the quality' of your voltage amplifier and suggest how it could be improved.

Answer 1

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