Analog Integrated Circuits

Linear Computational Circuitry

35 questions By Tony R. Kuphaldt

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Question 34 of 35

Draw the appropriate wires in this diagram to complete the circuit for a differentiator circuit (the opposite function of an integrator circuit):

The particular opamp used in this circuit is an LM324 (quad) operational amplifier. Of course, you need only show how one of the four opamps within the IC may be connected to form a differentiator.

Reveal answer

Challenge question: given the single-supply configuration ( 9 volts only), this differentiator circuit can only respond to one direction of input voltage change ([(dv_in)/dt]). Which direction is this: positive or negative?

Notes:
As always with problems centered around a pictorial diagram, the solution is more apparent if a schematic diagram is drawn as a “map” first. Ask your students to explain how they transitioned from the original diagram, to their own schematic, back to a completed diagram.

Also discuss the similarities between differentiator circuits and integrator circuits. The two mathematical functions are inverse operations of each other. How is this symmetry reflected in the respective circuit configurations?
Question 35 of 35

Analog computers have been all but replaced by digital computers in modern electronic systems. Yet, analog computational circuits still enjoy certain advantages over digital circuits. Describe what some of the limitations of analog computers are, and why these limitations have led to their obsolescence. Also, discuss some of the advantages of analog computers, and why a designer might still choose to use an analog computational circuit in a modern system.

Reveal answer

Analog computational circuits are much less precise than their digital counterparts. On the other hand, analog circuits tend to be much simpler than digital circuits (for the same functions), and they are generally faster.

Notes:
I like to introduce analog computational circuits to beginning electronics students because of their elegant simplicity, and for the fact that they greatly help to “link” the abstract world of mathematics to real mechanisms. Students are generally excited to realize they can build an actual computer with just a handful of inexpensive electronic components.