Help with a voltage range converter with comparator

[GabrielM.]

Hi there, I'm trying to change a 0-3.3V input to a +-3.3V output with a comparator that has a reference of 1.65 but I can seem to be able to make it work. Does anyone know what I'm doing wrong?

[tipa]

 

Хай! С вашей схемой у меня не получилось, взял отсюда: https://monitorbank.ru/komparatory-napryazheniya/
Надеюсь, правильно вас понял...
Удачи!

[GGoodwin]

Hi GabrielM. and tipa,

The first thing to do is to provide the proper negative supply voltage to LM311. There are two ways to do this:

• The value of V4 can be changed from -3.3V to 3.3V.
• The value of V4 can be kept at -3.3V but the battery (symbol) must be reoriented/reversed.

Next, the circuit should be rewired so that the LM311 can function as intended. There are four options available to achieve the objective:

1. The LM311 is setup as a noninverting comparator so its output transistor is used as a common-emitter switch. To obtain a bipolar output, LM311's GND pin should be connected to the negative supply voltage (V-) not to circuit ground. The circuit output is taken from LM311's OUT pin which should be pulled up (by a resistor) to the positive supply voltage (V+). The precise value of the pull-up resistor depends on several factors such as switching speed and power dissipation, 1 to 10 kΩ will generally work for this particular case.
   
2. Same as in option 1 but the output state can be inverted by connecting the junction of R6 and R7 to LM311's IN+ and the output of function generator XFG2 to LM311's IN-.
   
   
3. The LM311 is setup as an inverting comparator so its output transistor is used as a common-collector (emitter-follower) switch. To obtain a bipolar output, LM311's OUT pin should be connected to the positive supply voltage (V+). The circuit output is taken from LM311's GND pin which should be pulled down (by a resistor) to the negative supply voltage (V-). The precise value of the pull-down resistor depends on several factors such as switching speed and power dissipation, 1 to 10 kΩ will generally work for this particular case.
   
   
4. Same as in option 3 but the output state can be inverted by connecting the junction of R6 and R7 to LM311's IN+ and the output of function generator XFG2 to LM311's IN-.

The most suitable configuration depends on the application circuit.

Again, I don't have the (Desktop) application version of Multisim. I am only a Free Subscription user of Multisim Live so the LM311 is not available to me. I just edited the circuit image that was posted, you can try building these modified circuits in Multisim and provide feedback if they work as expected.

Best regards,
G. Goodwin

[tipa]

Спасибо, дорогой! Как всегда толково и подробно и понятно. Вышла новая версия 14.3
Можешь поставить себе.