Emitter follower circuit online simulation in Multisim | applied electronics engineering


Emitter follower circuit online simulation in Multisim

By Applied Electronics - Saturday, July 30, 2016 No Comments
Here we show how to simulate emitter follower circuit in Multisim. You can use the online multisim simulator to do this example.

Below is the circuit of emitter follower amplifier which will be created and simulated in multisim. The circuit was taken from the book electronics principles by Bates and Malvino(example 10.6).

Emitter follower circuit

We want to find out Icq, Vceq and re in this circuit. The following is the hand solution to this problem.

The following multisim tutorial shows how to measure quiescent current and voltage in multisim.

First launch the multisim software.

With the username and password "multisim" launch the application.

Then create the circuit. Note: change the value of source voltage from 120Vrms to 20mV and frequency of the input ac voltage to 1KHz or more for realistic scenario. This is a mistake in the circuit below.

Place a probe on the collector terminal of the transistor to measure the quiescent current Icq. And place a multimeter to measure the quiescent voltage Vceq.

Emitter follower circuit online simulation in Multisim

Start the simulation and read the values of Icq and Vceq as shown.

Emitter follower circuit online simulation in Multisim

The values of the Icq from the probe is 427mA to 432mA but the calculated value from the book is 456mA. The primary reason in this simulation is that the voltage divider input voltage is less than 8V which was used in the book. You can measure this Vbb voltage at the intersection of the resistors R1 and R2.

The value of Vceq is 5.13V from the simulation but the calculated value is 4.7V and this is a significant difference. Again this is most probably because of the transistor base input voltage which should have been 8V as per the calculation above. But in the simulation circuit it is somewhere  7.78V.

Although the value of input voltage is 120Vrms and frequency is 60Hz as opposed to realistic values, they have little effect in the values of quiescent current and voltage because this is primarily a DC point analysis and not AC analysis. You can change the voltage and frequency of the source and you will not get any appreciable difference of the Q-point value for this circuit.

You can watch this whole design and circuit simulation in the below video:

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