HW 3 material

Question 1

What is a low-pass filter?

Answer 1

Resistor then Capacitor

Question 2

What is a high-pass filter?

Answer 2

Capacitor then Resistor

Question 3

How do you know what a band-pass filter’s input/output impedance is?

Answer 3

First stage resistor is output impedance
Second stage resistor is input impedance

Question 4

In general, what should the ratio be between input/output impedance to avoid loading the first stage?

Answer 4

R2 = 10 * R1

Question 5

If V_in > Vd, how do you find V_out, I_R, and I_d?

Answer 5

1) V_out = Vd = V_R2 since they are all in parallel
2) Use V_R2 to find I_R (V=IR)
3) Find total current (I = (V_in - Vd)/R)
4) Use I = I_R + I_d and solve for I_d

Question 6

If V_in < Vd, how do you find V_out, I_R, and I_d?

Answer 6

1) If V_in < Vd, no current can pass through the diode, so I_d = 0
2) Use loop rule, so V_in - VR - VR = 0, and solve for I_R
3) V_out = I_R * R

Question 7

Given this circuit, how would you find the critical frequency?

Answer 7

1) w_c = 1/RC
2) Use w = 2(pi)f and solve f

Question 8

What is the common voltage of a diode?

Answer 8

0.65V

Question 9

If V_in < Vd, how do you find I_d and V_out?

Answer 9

1) Since V_in < Vd, I_d = 0, and
2) V_out = Vd = V_in

Question 10

V_Z = 5.6 V – V_out? I_d?

Answer 10

1) Since resistors are equal, divider guarantees at least 6V are available to back-bias the Zener diode, so it will conduct and hold its voltage, and V_out, and V_Z. So, V_out = V_Z = 5.6V
2) Use loop rules to find I_1 and I_2, and since I_1 = I_2 + I_d, use that to solve I_d

Question 11

If Vd = 0, what are the voltages at A and B, and what is the current through the diode?

Answer 11

1) If Vd = 0, it acts like a wire, so V_A = V_B
2) Find total resistance
3) Find V_AB = V0 (R23/RT)
4) Use V_B and R3 to find current thru diode