The new voltage drop for the collector-emitter of the transistor is actually less! It was about 0.08V. Let's change the Rb resistor, from 68KΩ to 10KΩ, and let's see what happens. What happens if we choose a lower Resistor? Not necessarily bad if you are using amplifiers but no good for this case. For switching this means that the circuit that we want to command is going to receive less “electric force” so to speak. The new voltage drop for the collector-emitter of the transistor is actually more! It was about 1.32V. Let's change the Rb resistor, from 68KΩ to 100KΩ, and let's see what happens. What happens if we choose a higher Resistor? ( The mode selector will vary from multimeter to multimeter). If it's the 2n3906, then in the PNP socket and select the ‘PNP' mode.

If it's the 2n3904, then insert in the NPN socket and select the ‘NPN' mode. Connect the transistor to the collector, emitter and base sockets of the HFE measurement. A few results under certain conditions can be found on the datasheet.īut let's use the HFE measurement tool from the multimeter to find out an approximately value. It varies on conditions such as temperature, collector current, etc.

How much gain does the transistor has? It depends. The current Ic is proportionately dependent on the value of Ib it's translated to the following formula: Ic = Ib * HFE The more current that flows through Ib, the more current will flow through Ic, theoretically. The ratio between the collector current ‘ Ic‘ and the base current ‘ Ib‘ is called HFE gain (sometimes called β). The Collector Current − Continuous is 200mA, which is more than enough current to switch the LED (9.84mA). Since the maximum voltage is going to be 5V, the circuit doesn't reach any of the maximums of Collector−Emitter Voltage or Collector−Base Voltage. 2N3906, BJT PNP transistor with TO-92 package: 1 unit.2N3904, BJT NPN transistor with TO-92 package: 1 unit.In this tutorial, all the components are Through Hole. Requirements for Push Buttons Components and Devices What happens if we choose a lower Resistor?.What happens if we choose a higher Resistor?.

Bjt diagram