QUESTION 2 (a) A two-port active device with a feedback impedance, Z, and a voltage gain A,, is represented by Figure Q2

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Question 2 A A Two Port Active Device With A Feedback Impedance Z And A Voltage Gain A Is Represented By Figure Q2 1 (51.94 KiB) Viewed 27 times

Question 2 A A Two Port Active Device With A Feedback Impedance Z And A Voltage Gain A Is Represented By Figure Q2 2 (32.62 KiB) Viewed 27 times

QUESTION 2 (a) A two-port active device with a feedback impedance, Z, and a voltage gain A,, is represented by Figure Q2(a)(i). If Z, is the Miller Effect of the device at the input, and Z, is the Miller Effect at the output, for the circuit in Figure Q2(a)(ii) is to be the equivalent circuit of the active device, prove that: L (1) (ii) Z₁ (1-4)² Z and Z B F Figure Q2(a)(i) = (4-1) [6 marks] Figure Q2(a)(ii) B PRO (b) A common-source JFET amplifier circuit is shown in Figure Q2(b). The amplifier has the following parasitic and wiring capacitances that effect its performance at high frequencies: C 2.5pF, Cd 2.0pF, Cas 2.5pF, C1.0pF and Co=1.0pF Draw the high-frequency small-signal equivalent circuit of the amplifier. [3 marks] Compute the values of the total input resistance R, total input capacitance Ca total output resistance RT and total output capacitance CTO- [4 marks] (iii) Compute the values of the upper cutoff frequencies at the input and output circuits, fi and fit, and determine the effective high cutoff frequency [3marks]
Rais 1.01.2 (ii) 1.0μF www R₂ 2M02 VDD 1 R₂ 2MQ +20V RD 2.0k0 D Ar Rs 1.0k Figure Q2 (b) 1.0μF S100k -2.5m5 1.0μF Z₂ R₂ IkQ (c) Draw the low-frequency small-signal equivalent circuit of the amplifier shown in Figure Q2(b). [3 marks] (i) Calculate the cutoff frequencies determined by the coupling capacitor C₁ at the input and the coupling capacitor C, at the output. [3 marks] Determine the cutoff frequency determined by the by-pass capacitor Cs and the effective low frequency cut off. [3 marks]