ECE 252 Introduction to Electrical Engineering

Lesson 17. Solid State Devices Homework

Version S18

Homework partner name: ______Homework partner name: ______

1. Quickies:

a) A solid-state relay is sometimes called an opto-______.

b) A 300 Hz sinusoidal signal is input to an amplifier. Signals of 300 Hz, 600 Hz, and 900 Hz occur at the output. This amplifier has ______distortion.

c) What is the bandwidth of an amplifier with a frequency range of 100 Hz to 700 Hz? ______Hz

d) Amplifier stages are frequently coupled using (diodes, capacitors, inductors, resistors) to block DC offset.

e) What value of resistance should be used to terminate coax cable? ______Ω

f) Two amplifiers are cascaded. The first has a gain of 40. The second has a gain of 30. If the input voltage to the first amplifier is 5 mV, the output voltage of the second amplifier will be ______V.

g) It is usually good for an amplifier to have ______input impedance and ______output impedance.

h) The emitter ______type of transistor circuit has about the same output voltage as input voltage.

i) The common ______is the most popular type of transistor circuit to use as an amplifier.

j) Sketch and label anNPN BJT.

k) When looking at the spec sheet, Forward Voltage, Peak Forward Current, and Average Forward Current (or Steady Current) are probably the most important specs for a(n) ______.

l) When lighting an LED from a computer circuit, using a logic 0 to light the LED is preferred because logic 0 can sink more ______than logic 1 can source.

m) The forward voltage for a typical red LED is about ______V.

n) Real diodes have a forward voltage drop of about .7 V. These diodes are usually made out of ______.

o) Sketch a clamping circuit.

p) The minimum output voltage of an ideal clamping circuit will be ______V.

q) A flyback (or snubber) diode can be used to prevent ______kickback.

r) The impedance of an ideal diode in the forward direction is ______Ω.

s) The impedance of an ideal diode in the reverse direction is ______Ω.

t) The first harmonic (frequency) is also called the ______(frequency).

u) Audio amplifiers often have an output impedance of (.8, 8, 80, 800, 8000) Ω.

Signatures: ______

2. You have an ideal diode, a voltage source of1.2sin(ωt) V, and a 2.2 kΩload resistor. a) Sketch and label a half-wave rectifier circuit. b)Show the source voltage and the load voltage wave forms in a diagram, giving numeric values where appropriate.c) Explain how the circuit works. d) What is the peak current in the load?

a) b)

Signatures: ______

3. In problem 2, the ideal diode is replaced with a silicon diode. Repeat parts b), c), and d) of problem 2.

Signatures: ______

4. Repeat Problem 2(using the ideal diode) with a smoothing capacitor added.

a) b)

Signatures: ______

5. a) Sketch and label a full-wave rectifier circuit. Use ideal diodes and a 1.1 V rms source. b) Show the source voltage and the load voltage wave forms in a diagram, giving numeric values where appropriate. c) Explain how it works.

a) b)

Signatures: ______

6. a) Design, sketch, and label a battery charger circuit. Use a sinusoidal voltage source with a peak value of 13.5 V, an ideal diode, and a resistor. The battery to be charged is a 12 V automobile battery. Assume its voltage is always 12 V; that is, the voltage is not dependent on the level of discharge. Assume the diode’s maximum forward current is 80 mA. b) Select an appropriate resistor to get maximum charging while protecting the diode from overcurrent. c) What must the minimum PIV of the diode be?

Signatures: ______

7. An L660-04UD(15) red LED has the following specifications: Maximum forward current: 50 mA. Typical forward voltage: 1.9 V. Design, sketch, and label a holiday light set using 70 of these LEDs and an appropriate resistor connected to a 120V, 60 Hz power source. You need not show all the LEDs in your sketch. Specify the value of the resistor.

Signatures: ______

BONUS (No partial credit):VCC = 6.5 V, RC = 1.1kΩ, RB = 22 kΩ, iB = 35 + 20cos(70t) µA, ß = 72. Find iC, iE, and vo.

Signatures: ______