lab 9 2009 common-emitter amplifier

# lab 9 2009 common-emitter amplifier - LAB 8 COMMON-EMITTER...

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L AB 8: C OMMON -E MITTER A MPLIFIER I Objective and Background: This laboratory has three objectives: 1. To build a CE amplifier and measure the dc parameters, the ac input resistance, and the voltage gain under different conditions; 2. To observe and document the effect of signal frequency on the CE amplifier performance; 3. To test the effect of certain faults in a CE amplifier on the benchtop and in MultiSim simulated circuits. Recall that in a CE amplifier, the input signal is applied at the base and the output signal is measured at the collector. The emitter is common to input and output circuits, hence the name common-emitter. DC analysis of the circuit yields I E , the dc emitter current. The ac emitter resistance r e ' is computed as: r' = I e E 25 mV The amplifier loaded voltage gain A lv can be written: A Vout Vin R r R R R r R lv c e E C L e E = 2245 + = + ' || ' 1 1 where R c represents the ac collector resistance and R E1 is the swamping emitter resistance. When R E1 is 0 (non-swamped amplifier), the loaded voltage gain is: A R R r lv C L e = || ' The input resistance seen by the ac source is: ( 29 ( 29 R R R r R in tot ac e E ( ) || || ' = + + 1 2 1 1 β The low frequency response of the amplifier is determined by the coupling and bypass capacitors in the circuit. At low frequencies, these capacitors do not behave as “shorts” anymore and contribute to lowering the effective gain of the amplifier. The lower cutoff frequency is obtained when the amplitude of the output waveform is 0.7 times the amplitude measured in the passband. 1

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II Common-Emitter Amplifier Prelab The amplifier you will build and analyze is shown on the following graph. Vs 300 mV pp 4.7 k 1 μ C1 10 k 2N3904 47 C2 0.33 k 0.1 k 1 k C3 12 V 1. Show the dc equivalent circuit of the amplifier and compute the dc parameters listed in the table below: V B V E I E V C V CE Theory 2. Show the ac equivalent circuit of the amplifier. Use the 2N3904 transistor data sheet handed out
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lab 9 2009 common-emitter amplifier - LAB 8 COMMON-EMITTER...

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