Experiment 4 - The bistable Multivibrator II

How does a bistable multivibrator work?

Take a look at the visual explanations. All parts connected to the negative terminal of the battery (0 Volt) are shown in blue, all the components on a positive voltage (>0 Volt) are shown in red.

1. Step

Suppose, after connecting the battery, the LED1 lights up...

• The transistor T1 switches through.
• Throught the resistor R1, the base of the transistors T2 is pulled down to 0 Volt and blocks. The LED2 remains off.

Visual explanation of how of a bistable multivibrator works (step 1).

Also, nothing changes when you press the push-button switch S2, since the voltage at the point S remains positive.

2. Step

In a second step you press the push-button switch S1. Thereby a positive voltage is applied to the point R...

• The transistor T2 switches through and the LED2 lights up.
• Through the resistor R2, the base of the transistors T1 is pulled down to 0 Volt and blocks. The LED1 goes out.

Visual explanation of how of a bistable multivibrator works (step 2).

To return to the first state, you must now use S1.

In the next circuit you are introducing a capacitor as a coupling element...