A+ Answers


  1. Design a circuit to produce a rectangular wave of period 100 µs and 60% duty cycle.  Any capacitors used are constrained to the value of 1 nF.
  2. Explain why obtaining a duty cycle of 50% or less cannot be achieved using the ‘555’ circuit of FIGURE 2. Describe a method by which the circuit could be modified to give a duty cycle of less than 50%.
  3. FIGURE 3 represents a ‘555’ timer used to control a process.  The process should commence when the START switch is operated and then continue for a period of 15 seconds (T) or until the STOP switch is activated.

Design a circuit to meet this specification.

  1.  In FIGURE 4(a) the input voltage V in is swept from 0 to 5 V. The supply voltage is a single-rail 5 V.  Explain the shapes of the output responses of the two op-amps shown in FIGURE 4(b).

[TABLE E gives some further information on these op-amps.]

  1. Estimate the maximum frequency of a sinusoidal input signal of 10 mV peak, for distortion-free output, when applied to an op-amp circuit of closed-loop gain of 100, if the op-amp used is the:
  2. a) TL072
  3. b) TLV2362