homework assignment

Homework Assignment

1 Problem

1 Consider the design of a monostable 555 timer circuit.  Use the formulas discussed in class to answer the following problems:
a. Given a capacitor with a capacitance of 0.1uF, calculate the resistance needed to generate a pulse of time t=2 seconds.

b. Find t given C=1uF and R=1MΩ.

c. If the 555 timer is triggered while the output state is still high, what will happen to the output of the timer.
Problem 2

Consider the design of an astable 555 timer circuit.  Use the formulas discussed in class to answer the following problems:
a. Find t, th and tl, for a 555-timer circuit with R1=1kΩ, R2 = 1kΩ, and C = 1uF.

b. Calculate the frequency of the output signal of a 555-timer circuit with t = .001s.

c. Calculate the period and frequency of a 555-timer circuit with R1=2kΩ, R2=5kΩ, and C=0.01uF.
Problem 3

a. The reset and trigger pins on the 555-timer IC are said to be active low.  What does this mean?

b. If Vss= 15V, what voltage, as seen by the threshold pin, must the capacitor reach before the output of the 555-timer returns to zero, and the capacitor can discharge?

c. An LED circuit is connected to a 555-timer such that the timer is sinking the current through the LED circuit.  During what point of the output signal, either high or low, is the LED illuminated?  Explain your answer.
Problem 4

Refer to the datasheet for the TLC555 timer IC to answer the following questions.  The TLC555 timer is a variant of the LM555 timer discussed in class.
a. What is the minimum supply voltage required for the TLC555 to operate?

b. What is the typical sink current for the TLC555?

c. What is the typical source current for the TLC555?