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Step 4.051P (a) For small signal analysis replace the DC current source by open circuit and diode with dynamic resistance. Assume the diode is conducting (i) Open circuit the load (ii) Replace the current source as open circuit (iii) Replace the voltage source and diode with equivalent resistance d Draw the small signal equivalent + R Figure Step Calculate the expression for the equivalent resistance Step Apply voltage division rule to calculate the gain of the R R R R+r, Calculate the value of diode resistance rd 2 2(0.025) 0.05 I Step Write the table find for different values of Table 0.05 R I 0 8 0 10-3 0.167 V 10-2 0.667 V 0.952 1 0.995 10 0.9995 Step (b) If the signal current is to be limited to +10 % change in diode voltage is given by whose value between 0.9 and 1.1. Calculate the change diode voltage for 0.9 In (25) -2.63 mV Step Calculate the change diode voltage for is In(1.1) (25) =2.38 mV Where, the input voltage varies in between 2.63 mV to +2.38 mV for signal current is limited to 10% of dc bias current. Thus, the largest signal voltage Step For input = 10 mV the output current is, 5 mV 0.5 Each diode carrying current of 0.25 for this to be at most 10% of current, dc current in each diode must be 2.5 Thus, the minimum value of is Step (c) For mA, 0.5 mA and for maximum signal of 10% - 0.05 mA 0.1 mA The total current each diode is mA The corresponding maximum is, =0.1 mA V Thus, the largest possible output signal is V Step The corresponding peak input can be found by dividing V. by transmission factor of Calculate the peak input voltage. 0.995 V 1.005 Thus, the peak put voltage is .005