Experiment 1 - The Transistor as a Switch

What exactly is a multivibrator? In the literature you will find answers like: "multivibrators are cross-coupled digital circuits." or "A multivibrator consists of two mutually coupled electronic switches." But what does it mean?

First, do you pose yourself the question of what an "electronic switch" or "digital circuit" is.

Circuit of a saturated transistor. (Enlarge)

Circuit diagram of a saturated transistor circuit.

In the circuit shown, you recognize a transistor circuit. The transistor is connected such that it acts as an electronic switch...

• If the push-button switch S1 is open, the transistor is locked and the light emitting diode LED1 is dark.
• If you close the push-button switch S1, the transistor is "saturated" and switches through completely. The LED lights up.

The circuit has two states! Therefore, it is also called a digital circuit.

In the next experiment, you couple two digital circuits...