how to use transistor logic instead of op-amp in my gate drive circuit?

[krishna1331]

i am using a gate drive circuit by using an opto coupler 6n137. i want to get a +/- 12v supply at output for driving the gate of mosfet. so for that i have used an op amp after the output of opto coupler(pin 6). at pin 6 we get a 0-12v ouput pulse and that when passed through a comparator lm 311 we get the +12 to -12v output pulse. so what i need is how to use transistor logic instead of tht comparator logic of lm 311, so that i get +12 to -12v output pulse.
i am attaching the scanned image of the gate drive circuit.

 

[ericgibbs]

i am using a gate drive circuit by using an opto coupler 6n137. i want to get a +/- 12v supply at output for driving the gate of mosfet. so for that i have used an op amp after the output of opto coupler(pin 6). at pin 6 we get a 0-12v ouput pulse and that when passed through a comparator lm 311 we get the +12 to -12v output pulse. so what i need is how to use transistor logic instead of tht comparator logic of lm 311, so that i get +12 to -12v output pulse.
i am attaching the scanned image of the gate drive circuit.

hi,
Have you considered an MC1488 line driver, power it with +/-12 or 15V, use 5V input to get +/-12V swing.

 

[krishna1331]

thnks.. for info abt mc1488 driver.. i will check tht out.
but i need to use only transistor logic to get +/- 12v for mosfet

 

[ericgibbs]

thnks.. for info abt mc1488 driver.. i will check tht out.
but i need to use only transistor logic to get +/- 12v for mosfet

The 1488 has a +/- 12V output.

EDIT;
Look at this dwg.

 

[Grossel]

thnks.. for info abt mc1488 driver.. i will check tht out.
but i need to use only transistor logic to get +/- 12v for mosfet

I guess you don't trying to use ttl's. Then I have a possible solution:

I was a little quick. The switch symbol on my drawing represents the output of your 6n137.

 

[on1aag]

If you close that switch both transistors will be blown up
unless you insert a resistor from the collector of the pnp
to the base of the npn and a second resistor from the
base of the npn to the -12 volt terminal.

on1aag.

 

[Grossel]

If you close that switch both transistors will be blown up
unless you insert a resistor from the collector of the pnp
to the base of the npn and a second resistor from the
base of the npn to the -12 volt terminal.

on1aag.

American?

In europe, this is the way resistors is represented. By a rectangle

 

[ericgibbs]

American?

In europe, this is the way resistors is represented. By a rectangle

hi,
I think you misunderstood, the red resistors are the ones on1aag recommended.

 

[Grossel]

hi,
I think you misunderstood, the red resistors are the ones on1aag recommended.

Ah - of course. I was drawing too fast this time. Sure there should be resistors there

 

[Hero999]

American?

In europe, this is the way resistors is represented. By a rectangle

Yes, and it's the best way in my opinion as it's easier to draw a retangle than a zigzag which could also be confused for an inductor if the person isn't very good at drawing.

 

[Willbe]

For 0-5v converted into -12v to +12v you need a voltage gain of +(24/5) and a negative level shift of either 2.5v or 12v, depending on where you put the shifter.

How much output load capacitance you're driving at what speed determines the current (and power) output needed.