Testing of LM 311.

Thread Starter

saranya ajesh

Joined Sep 26, 2011
4
hi,
I have an LM 311 IC with me. I need to check whether it is working or not.
I don't have any testing equipment with me. Please guide me regarding the same.
 

SgtWookie

Joined Jul 17, 2007
22,210
Here is a simple test circuit:



When VR1 is about mid-position, a small movement one way or the other should turn the LED on and off.

This is just a very quick and informal test. If you want to know if it is functioning according to manufacturer's specifications, you will need test equipment.
 

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Thread Starter

saranya ajesh

Joined Sep 26, 2011
4
Sir,
Thank you for your reply. I implemented this circuit and got output. But I have doubts about its output section. Why we are connecting the cathode of LED to the output. Is it in reverse biased condition? [/COLOR]
 

Thread Starter

saranya ajesh

Joined Sep 26, 2011
4
Sir,
Thank you so much for your reply, it helped me a lot. But sir I have one doubt about its output section. Why we are connecting the out put to the cathode terminal of the LED
.

Here is a simple test circuit:



When VR1 is about mid-position, a small movement one way or the other should turn the LED on and off.

This is just a very quick and informal test. If you want to know if it is functioning according to manufacturer's specifications, you will need test equipment.
 

SgtWookie

Joined Jul 17, 2007
22,210
Pin 5 is the output of the comparator. It is an open-collector output. It can sink current from pin 5 to pin 6, but it cannot source current from pin 5.

An LED will only light up if current flows through it in one direction. The anode must be more positive than the cathode in order for it to light.

As shown, when the output is turned ON while adjusting VR1, current is sunk from the 9v supply V1 via the resistor R5 through the LED D1 to pin 5; this causes the LED to illuminate.
 
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