Transistor as a switch works same as NOT Gate. It is define as a device whose output is always the complement of its input. The input is represented by A and the output variable by X. the expression for the output is X= A. this is read as “X” is equal to A bar.
Component Required :
- Transistor (BC 547)
- Resistance (10K, 470 ohm)
- Momentary switch(2 pcs)
- Battery- 9v
- Dotted PCB
- Connecting wire
A transistor is a semiconductor device which is made by sandwiching two PN- type semiconductor. Transistor has three terminal collector, base and emitter. The transistor is use for the purpose of switching and amplification. There are two type of transistor, first is p-n-p and second one is n-p-n. in the AND Gate we are used n-p-n transistor.
This is a two terminal resistive device which is used to oppose the following the current in the circuit. Resistance is made up of carbon material. It never contain positive or negative terminal. We can use its any of the side as to oppose the current in appropriate manner. Resistance comes in different values which we used according to our need.
Led (Light Emitting Diode) :
Led stands to light emitting diode. This is mostly use for lighting purpose or as a indicator of the circuit .this is a two terminal device Here in the image as you can see the long tail is positive and the short tail is negative.
Led Input voltage : 3 volt Dc.
Led is always connected with 220 or 470 ohm Resistance.
A discrete NOT Gate may be realized using a switching transistor as shown in fig. the input to the gate may be 0v or 5v. when A= 0v transistor T is reverse biased & therefore, remains OFF. As no current flows through R, no voltage drop across R. Hence, the output voltage X= +5v. when the input A= +5v, T is ON & the output voltage X= sVce(sat) is nearly equal to 0v.