The circuit diagram in Figure 1 shows a voltage source V, and resistance R connected to an amplifier with a power gain A

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The Circuit Diagram In Figure 1 Shows A Voltage Source V And Resistance R Connected To An Amplifier With A Power Gain A 1 (151.28 KiB) Viewed 31 times

The circuit diagram in Figure 1 shows a voltage source V, and resistance R connected to an amplifier with a power gain Ap, which is in turn connected to an output load R₁. The amplifier is matched for maximum power transfer with the source and the load. The noise generated by the amplifier is described by a noise voltage generator en and a noise current generator in. The circuit operates at a temperature of 290 K. Vcc en Ap Rs RL Vs Figure 1. (a) Determine an expression for the optimal resistance for the source if the least amount of noise is to be added by the amplifier to the output. (b) Considering the circuit in Figure 1 in the case where R = R₁ = 75 02, and the amplifier power gain Ap = 10,000. The input and output resistances are matched to the load and source for maximum power transfer and the noise properties are en = 3 nV/√Hz and in = 4 pA/√Hz. The input is a double sideband amplitude modulated signal formed by a baseband signal of bandwidth 10 kHz modulated onto a 50 kHz carrier. The input signal power level is -106 dBm. Determine: (i) the noise power at the output; (ii) the signal to noise ratios at the input and output, and the noise figure of the amplifier.