# Category: microelectronics sedra and smith chapter 4 #### 10.5 Find Cde, Cje, Cπ , Cμ, and fT for a BJT operating at a dc collector current IC = 1 mA and a CBJreverse bias of 2 V. The device has τF = 20 ps, Cje0 = 20 fF, Cμ0 = 20 fF, V0e = 0.9 V, V0c = 0.5 V,and mCBJ = 0.33.

... #### Example 10.7 The high-frequency response of an amplifier is characterized by the transfer function Determine the 3-dB frequency approximately and exactly.

... #### 4.69 Consider a half-wave rectifier circuit with a triangular-wave input of 5-V peak-to-peak amplitude and zero average, and with R = 1 k . Assume that the diode can be represented by the constant-voltage-drop model with = 0.7 V. Find the average value of v O .

... #### 4.68 Using the exponential diode characteristic, show that for v S and v O both greater than zero, the circuit of Fig. 4.23(a) has the transfer characteristic v O = v S −v D at i D = 1 mA −V T ln v O /R where v S and v O are in volts and R is in kilohms. Note that this relationship can be used to obtain the voltage transfer characteristic v O vs. v S by finding v S corresponding to various values of v O .

... #### 4.67 Consider the half-wave rectifier circuit of Fig. 4.23(a) with the diode reversed. Let v S be a sinusoid with 10-V peak amplitude, and let R = 1 k . Use the constant-voltage-drop diode model with V D = 0.7 V. (a) Sketch the transfer characteristic. (b) Sketch the waveform of v O . (c) Find the average value of v O . (d) Find the peak current in the diode. (e) Find the PIV of the diode.

... #### 4.66 It is required to design a zener shunt regulator to provide a regulated voltage of about 10 V.The available 10-V, 1-Wzener of type 1N4740 is specified to have a 10-V drop at a test current of 25 mA. At this current, its r z is 7 . The raw supply, V S , available has a nominal value of 20 V but can vary by as much as ±25%. The regulator is required to supply a load current of 0 mA to 20 mA. Design for a minimum zener current of 5 mA. (a) Find V Z0 . (b) Calculate the required value of R. (c) Find the line regulation. What is the change in V O expressed as a percentage, corresponding to the ±25% change in V S ? (d) Find the load regulation. By what percentage does V O change from the no-load to the full-load condition? (e) What is the maximum current that the zener in your design is required to conduct? What is the zener power dissipation under this condition?

... #### 4.65 A zener shunt regulator employs a 9.1-V zener diode for which V Z = 9.1 V at I Z = 9 mA, with r z = 40 and

... #### 4.64 Provide two designs of shunt regulators utilizing the 1N5235 zener diode,which is specified as follows: V Z =6.8 V and r z = 5 for I Z = 20 mA; at I Z = 0.25 mA (nearer the knee), r z = 750 . For both designs, the supply voltage is nominally 9 V and varies by ±1 V. For the first design, assume that the availability of supply current is not a problem, and thus operate the diode at 20 mA. For the second design, assume that the current from the raw supply is limited, and therefore you are forced to operate the diode at 0.25 mA. For the purpose of these initial designs, assume no load. For each design find the value of R and the line regulation.

4.64 Provide two designs of shunt regulators utilizing the 1N5235 zener diode,which is specified as follows: V Z =6.8 V ... #### 4.63 Design a 7.5-V zener regulator circuit using a 7.5-V zener specified at 10 mA. The zener has an incremental resistance r z = 30 and a knee current of 0.5 mA. The regulator operates from a 10-V supply and has a 1.5-k load. What is the value of R you have chosen?What is the regulator output voltage when the supply is 10% high? Is 10% low? What is the output voltage when both the supply is 10% high and the load is removed? What is the smallest possible load resistor that can be used while the zener operates at a current no lower than the knee current while the supply is 10% low? What is the load voltage in this case?

4.63 Design a 7.5-V zener regulator circuit using a 7.5-V zener specified at 10 mA. The zener has an incremental ... #### 4.62 A9.1-Vzener diode exhibits its nominal voltage at a test current of 20 mA. At this current the incremental resistance is specified as 10 . Find V Z0 of the zener model. Find the zener voltage at a current of 10 mA and at 50 mA.

4.62 A9.1-Vzener diode exhibits its nominal voltage at a test current of 20 mA. At this current the incremental resistance ... 