1. Show that the diode is a non-linear device by analytically proving that superposition fails, and create an example

that clearly demonstrates this.

The following problems deal with circuits using op-amps to realize “ideal rectifiers” or “superdiodes”.

These improve
upon the basic op-amp circuit first shown in Fig. 4.29 (pg. 220) and discussed later in section 18.9.1 when more
advanced circuits are discussed. This is a chance for you to apply some of your op-amp knowledge to sophisticated
non-linear circuits. 4.3 and 4.4 are exercise problems, so they have answers. The objective is not to “get the right
answers” but to confirm your understanding of the circuit.

2. Work the two exercise problems, 4.3 and 4.4 and discuss which of the four basic diodes models they realize.

3. Do Exercise problem 18.29 on page 1818 (bonus pg. 3-72).

Do Exercise problem 18.30 on page 1818 (bonus pg. 3-72).

Compare these two circuits, explaining what makes them “superdiodes” and why the second one is superior to
the first.

Note: A textbook reference for section 18.9 containing 18.29 and 18.30 is included at the end of this homework.

5. Consider the following equivalent circuit employing a silicon signal diode to be used in a small-signal
application.

a) Find an expression for this circuit’s high-pass -3dB corner frequency. Assume the diode has an ideality factor
n=2,
1 Rk 
, capacitor is unspecified.

b) From your results for (a), design the circuit by finding a value for C such that
3 100 dB f Hz  
if the diode’s
bias current can be adjusted anywhere between
10 A 
and
1mA
. Indicate what the actual corner frequencies
are for the two current extremes.