BME102: A silicon diode has a forward voltage drop of 1.4 V for a DC current of 140 mA: Essentials of Bioelectronics Assignment, SUSS, Singapore

Question 1

(a) A silicon diode has a forward voltage drop of 1.4 V for a DC current of 140 mA. It has a reverse current of 4 µA for a reverse voltage of 12 V. Apply the correct formulae to calculate the following.

(i) The bulk and reverse resistance of the diode.

(ii) The AC resistance at forwarding DC current of 4.5 mA and 45 mA, respectively.

(b) Describe the working principle of a bridge rectifier.

Question 2

(a) The silicon transistor circuit shown in Figure Q2(a) has β = 200.

(i) Find IC.

(ii) Determine VC, VE, and VCE.

(b) Demonstrate how a transistor can be used as a switch, with the help of necessary diagrams.

Question 3

(a) Explain how Op-Amp can be used as a zero-crossing detector. Support your
answer with the help of diagram(s).

(b) When a differential amplifier has a differential input voltage of 5 mV, the output voltage is 14 V. When the common-mode voltage is 3 V, the output voltage is 12 mV. Use the above-given information to answer the following.

(i) Draw the circuit of a differential amplifier.

(ii) Calculate the differential-mode gain.

(iii) Calculate the common-mode gain.

(iv) Determine the CMRR.

(v) Calculate the thermal noise voltage of a 75 k resistor in room
temperature (300K), measured by an instrument with 50 kHz bandwidth.

(vi) If the resistor in Q3(b) forms the input to an amplifier that has a gain
of 106, determine the noise voltage at the output of the amplifier.