The Bjt Inverter

The BJT Inverter


Neftali Diaz Alvarez and Pedro Juan Mojica


Turabo University of Puerto Rico- Electrical Engineering Department
IEEE, member, ELEN 433 students



Abstract- Theexperiment about to BJT inverter we learned the behavior when is applied voltage in the base and collector a same time with different voltage, found β a similar form to BJT common- emitter and function liketo a switch. We observed that no matter increased voltage at the base, will always be limited by Vcc and demonstrated that worked like to logic gates. If the input to invert was a logical 0, theoutput logical is 1 and vice versa. In the oscilloscope we studied different signals form to view the behavior input signals, out signals, when is saturate and how limited the base voltage.Introduction
The basic element of logic circuits is the transistor switch. A schematic of such a switch is shown. When the switch is open, Ic= 0 and Vo = VCC. When the switch is closed, Vo = 0 and iC = VCC=RC.In an electronic circuit, mechanical switches are not used. The switching action is performed by a transistor with an input voltage switching the circuit, as is shown.
When Vi = 0, BJT will bein cut-off , Ic = 0, and Vo = VCC (open switch).
When Vi is in high state, BJT can be in saturation with Vo = VCE = Vsat=0.2 V and iC = (VCC Vsat)=RC (closed switch).
The above BJT circuit is alsoan inverter. Let's assume that the low state is at 0.2 V and the high state is at 5 V and VCC = 5 V. When the input voltage is low Vi = 0.2 v. BJT will be in cut-off and Vo = VCC = 5 V (high). Wheninput voltage is high, with proper choice of RB, BJT will be in saturation, and Vo = VCE = Vsat= 0.2 V (low).
Procedure
In order to determine the β of the transistor, connect the following circuit:Figure 2: Circuit to Measure β.
(Refereed to steps 1 and 2)
Measure the voltage across the collector resistor VRC and the base to emitter voltage VBE. Then calculate β.
To demostrate the...