Contents
How does a transistor work as a diode?
Since a bipolar transistor is essentially two diodes, it can function as such. However, since bipolar transistors are not designed to be used as diodes, using them as diodes might cause a problem in terms of current and other ratings. Use dedicated diodes for typical diode applications instead of bipolar transistors.
Can we use BJT as diode?
Take a look at a BJT datasheet and you will see that the maximum reverse B-E voltage is low, usually quite a bit lower than the maximum C-E voltage. If you can live with the low reverse voltage, then a BJT with colletor and base shorted can be used as a ordinary silicon diode.
Is transistor a diode?
Put simply, a diode is a two-terminal semiconductor device and a transistor is a three-terminal semiconductor device. A diode can allow the flow of current in one direction while blocking the flow of current in the other direction.
Can we use two semiconductor instead of a diode?
Summary: Two back-to-back PN diodes can’t function as a single BJT because transistor’s functionality requires semiconductor only Base region.
How does base biasing work in bipolar junction transistors?
Any increase in current flow through RE will increase the magnitude of negative voltage applied to the base circuit, decreasing the base current, decreasing the emitter current. This decreasing emitter current partially compensates the original increase. Note that base-bias battery VBB is used instead of VCC to bias the base in the figure above.
How does temperature affect the bias of a transistor?
Variations in bias due to temperature and beta may be reduced by moving the VBB end of the base-bias resistor to the collector as in the figure below. If the emitter current were to increase, the voltage drop across RC increases, decreasing VC, decreasing IB fed back to the base.
How is bias reduced in a collector-feedback resistor?
Collector-Feedback Bias. Variations in bias due to temperature and beta may be reduced by moving the VBB end of the base-bias resistor to the collector as in the figure below. If the emitter current were to increase, the voltage drop across RC increases, decreasing VC, decreasing IB fed back to the base.
What happens to base current when bias voltage is reduced?
It won’t get much above 0.7V, but as bias voltage is reduced the Base current decreases so it has less effect. If current going through the divider is much larger than the Base current it will set the bias voltage fairly accurately.