• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Tl494 half bridge smps


New Member
Hello everyone,
I was studying a tl494 based half bridge smps
I came across the current sense section opamp pin 15 & pin16
Now pin16 is connected directly to the ground
But there is some arrangment made to pin 15

I have drawn a part of it
Please can anyone help me what is a purpose of “103 trimpot” and why does the transistor “ 2n2222a” is also used which Is connected to microcontroller pic18f452



Well-Known Member
Most Helpful Member
The TL494 has two "error amplifiers" pins 1,2 and 15,16 with the output on pin 3. The two amplifiers are the same and can do any job. Usually one is usd to watch the output voltage and the other is used for over current limit.

The two resistors (0.1) are current sense. It is over current limit. The computer pulls up on pin 15 to change the point where the TL494 goes into current limit.


New Member
So why is the trimpot used then???
And i am sorry sir i did not understand your last statement
“The computer pulls up on pin 15 to change the point............................”

Latest threads

EE World Online Articles