7. Electronics – 7.5 Capacitor/transistor circuits For the teacher 7.5 Capacitor/transistor circuits Basic information The “capacitor/transistor” electronic circuit is a very good example and collecting ideas for providing some initial understanding of the possibilities and complexity of electronics. Observing After the switch is closed, the LED will emit light more or less and documenting immediately. When the switch is opened, the LED will continue to emit light for some time, although the transistor base is no longer connected to the positive pole. The light grows dimmer until it goes out completely. Analyzing When the switch is closed, the capacitor will be charged. The charging and reflecting takes very little time. While the capacitor is being charged, current will flow through it. When the capacitor is fully charged, the flow of current through the capacitor will be cut off and the current flows to the transistor base, switching the transistor on, which allows the flow or current through the collector-emitter section of the transistor: The LED will light up. After the switch is opened, the flow of current from the battery to the transistor base will be cut off. Because the positive side of the capacitor is still connected to the transistor base, the capacitor discharges and keeps the transistor switched on. Once the capacitor is discharged, there is no more flow of current to the transistor base and the transistor (collector-emitter) will be switched off: The LED goes out. Space for notes © Siemens Stiftung 2019. Content licensed under CC BY-SA 4.0 international Page 1 of 1 .