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For the current-mirror-loaded BJT differential amplifier in Figure 1, let I = 0.6 mA, VA = 120 V, and β = 120. Find differential gain Ad = vo/vid and differential input resistance Rid. vid = vB1 - vB2

For the current-mirror-loaded BJT differential amplifier in Figure 1, let I = 0.6 mA, VA = 120 V, and β = 120. Find differential gain Ad = vo/vid and differential input resistance Rid. vid = vB1 - vB2

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For the current-mirror-loaded BJT differential amplifier in Figure 1, let I = 0.6 mA, VA = 120 V, and β = 120. Find differential gain Ad = vo/vid and differential input resistance Rid. vid = vB1 - vB2

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Figure Q2 shows a BJT differential amplifier stage that uses a tail resistor, RO, to provide a bias current, IQ. Transistor parameters are VBE(on) = 0.7 V, β = 100, and VA = ∞. Also, Vcc = 15 V, −VEE = −15 V, RO = 56 kΩ, and RC = 15 kΩ. Figure Q2: Differential Amplifier (a) To calculate the transistor Q-points, what are the values you would assume for vB1 and vB2 ? (b) Determine the bias currents, IC1 and IC2, of the amplifier. (c) For a single-sided output, determine the differential-mode voltage gain (Ad), the commonmode voltage gain (Acm), the differential input impedance (Rid), the common-mode input impedance (Ricm), and the common-mode rejection ratio (CMRR) in dB for the differential amplifier. Assume a signal source resistance of 50 Ω on each input. (d) Will changing RC affect the amplifier CMRR? (e) Suggest two changes to this amplifier each of which would allow the CMRR to be increased. For each, give a reason why the change would have the desired effect.

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Question 1 (Differential amplifiers) (20) The transistors of the differential pair of Figure 1 are supposed to be matched. Assume that for both transistors VBE = 0.7 V and β = 100. The two transistors are biased for Vin1 = Vin2 = 0 V. Find gm1, gm2, rπ1 and rπ2. (4) For vin1 = vid/2 and vin2 = −vid/2, where vid is a small signal differential input, find the magnitude of the differential gain ∣(vo1− Vo2)/vid if the output is taken differentially. (4) Find the differential mode input impedance Rid. (4) For vin1 = vin2 = vicm, find the common mode input resistance Ricm. (4) Find the magnitude of the single ended common mode gain |vol/vicm | and calculate the single-ended Common Mode Rejection Ratio CMRR if the resistance connected to the collector of Q2 has an error of ±1%. (4) Figure 1

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Q1. The circuit below has I = 0.5 mA, VA = 30 V, and β = 150. (a) Specify what is this circuit? (b) Find Gm, Ro, Ad and Rid. (c) (b) If the bias-current source is implemented with a simple npn current mirror, find REE, Acap and CMRR. (d) If the amplifier is fed differentially with a source having a total of 20 kΩ resistance (i.e. 10 kQ in series with the base lead of each of Q1 and Q2), find the overall differential voltage gain.
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