AND Gate using Transistors on a Breadboard
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- เผยแพร่เมื่อ 29 มี.ค. 2020
- This circuit shows the working of a logical AND gate using two transistors.
When both the switches are open, there is no current flowing through the transistors and hence the output is LOW. In this state, the LED is OFF.
When one switch is closed and the other is open, the respective transistor is either ON or OFF. However, the current cannot flow through the transistors as they are connected in series. Hence the output is LOW. Again, in these states, the LED is OFF.
When both the switches are closed, both the transistors are ON and the current flows through them. Hence the output is HIGH and the LED turns ON.
Your Videos are great keep on going:)
Thank you
It is amazing. because it's on positive side of circuit.
Great video! I’m new to EE, could you please explain why we need the 1K resistor between T-2’s emitter and the negative rail? Thank you :)
Thank you for watching my videos. The 1K resistor works as a pull down resistor to create a zero output when one of the inputs is zero.
@@electronics_champI looked everywhere, and this solved my problem of the LED dimly lighting up whenever I pressed the second button on its own. Thank you!
What is need of collector to ground resistance ???
great video, thanks! why do we need to make connection between emitter of T2 to negative rail?
When using an NPN transistor as a switch, it is best to use it to pull down current by using a resistor. This is done by connecting the emitter to the lowest potential (GND). This configuration enables the transistor to control the flow of current from the collector to the emitter, thus acting as a switch. Hope this helps!
im getting some current flow between the base and emitter for the second transistor, is there any reason why this would be? for example, if i have NO Vcc but have A high, then the LED glows (although dimmer, presumably just from the 10k ohm resistor on a input)
ive seen that this is because the current at the emitter is the sum of the base and collector currents. one way of fixing this is by putting the load before the transistor, but if i was trying to create multiple gates in series to form a logic circuit then this means that i have to effectively build my circuits backwards? i would like to know if there is a way i can fix this.
it seems to me that you have used a method of putting the load before the transistors which im not criticising as it works perfectly fine for the purpose of this video. but would there be any way to do what i am trying to achieve?
The LED glows because of these 3 reasons:
*Leakage Current* : Tiny current can flow even when the transistor is off.
*Input High without Vcc* : If A is high without Vcc, it can cause current to flow.
*Resistor on Input A* : The 10k ohm resistor on A could allow some current to flow, lighting up the LED.
This can be fixed by increasing the 10k resistor to a convenient resistance for your circuit. But it is important to test the changes first.
Everywhere I read, the load (in my case a solenoid) "must" be on the collector side. Her on the e-side. Is it ok to put a solenoid on the e-side?
This link may help you decide where to place the load: electronics.stackexchange.com/questions/38285/connect-load-to-collector-or-emitter-of-transistor
@@electronics_champ Wow, thats the perfect answer. Many thanks!
I'm a bit confused. Why would you even need transistors in this case for an AND gate? Could you just have the buttons in series, then a resistor, then the bulb, then ground, to make an AND gate as well (though I know the point of the video is to use transistors)? Also, does the voltage needed to activate the transistors differ from the voltage needed to light the bulb?
And where do you buy these transistors from? I don't know why but I can't seem to find discrete CMOS MOSFETS for a breadboard anywhere.
Hi, you’re correct. The method you mentioned can be used to build an AND Gate. However, this method doesn’t allow the output to be controlled by input from other circuits. If you want to turn on an LED when the output of two other circuits is high, then you’ll need to build the AND Gate using transistors.
As for the components, I buy them from an offline store. You can check for them from websites such as Amazon or something like that.
why when I did that it's like an or logic gate?😢
Nice
I have a question
I didn't use any resistor in tinkercad when second transistor was turned on led is turned on even power is not reaching does resistor serve some special purpose other than current limiting
The resistors help ensure proper biasing of the transistors and limit the current to prevent damage to the components. For example, the 1K resistor works as a pull-down resistor to create a zero output when one of the inputs is zero.
@@electronics_champ thanks sir
There is a major flaw in this design(google abt it). when s2 is pressed there is voltage , it may not turn led on but for digital purposes there appears voltage
Thanku sir
Sir my one is not working, whenever I touch S2 only bulb glows
The exact same is happening here
Is the LED glowing when you press only one switch (S2)?
@@electronics_champyess
can i make 6 input ?
I have seen 3 input AND Gate. I need to check about 6 input AND Gate.
How to do it Using three transistor
You can make a 3 Input AND Gate using 3 Transistors. The circuit diagram is available at this link - lh3.googleusercontent.com/tYUZDJbKlkgUAxqrx-4uI_Zy8oGl4NsvzPSlPY0UsA1ME5sn1PjjIwl8sR0Xn5dHHvQ3OpjOR4bOR7B9Q5LFuIz661CFxAjmgXygpZ8rqkRG4_i_fk_pOgSBynXGQ-gryTVoyt-tKGKmYJKBUeHhNl0YRdxBRfW07-imu3Z-VUbdxUpKtA6-ksp5tCXH0uxAP1CDlXGcuGy4Zx1eY2ln3Sh5Tn73JZYxmnFKDGBXHmfCeqNLqu7xp0tHSmRnwkJkmmy9VkbNPiSPnRjVVpXGppMzv-Y4kb1HPj8KQppvXLTdq2xdheSlhJn2UgYOnA7A0YY1ULQyb8WsiDFMemCn4yzHJwmAJQXURJ_NncRrE9EbgnpKLHViVw6-5jQXh1o97Hc5Q0Qq-LVnB6bCmoaMR9Y4eBemI0rS5yUC_W9_TARBHq3kSB4ZflFcYSmQRV7pNn64mxuWEnjnZwSpBwW2pTtTOtWYTIDFcOu0vojbq7B3YeeGOJq58HF9jIINzq6m-gsDXfDb9hO38yFVTD_nyLNePlv7A431tGKgfjfFV7l2OlrBq9mknW7AzuaqZJAz6L7lqgrWHiu1ibQ3DD5_mIArv_x4aCjslBHbbQfjumPgFvhyfFYOHDQAVApqCaWgbQF1fWw46TyQZFQv3VKHcot1-GbQ5WngqkhAFfp1YsXzCHAe2_pp0JWZklNNYo_igLxGN7D0aArkqmM9nPfJ1Eqnc7TH_WVVhf5o_Qv5UuGTAMnbHlpD2TNgwt6Rog=w138-h220-no
I made it white one
how to turn and gate into xand gate
XAND and XNAND do not give extra functionality. We have XOR and XNOR.
@@electronics_champ ok thank you
Great question. AND and OR gates and INVERTER gates are the most useful ... XOR and XNOR gates have their purposes if those above three don't accomplish creating a XOR or XNOR function where extra hardware components increase! 👍