PWM motor with parallel BJT

[Fercho7]

Hello forum. I am designing a 90v 4.5A pwm. In a preliminary test I used three tip35c directly with an arduino with the motor without load and it works. Now to add load I want to make a good circuit to manage four tip35c, for that I took the minimum gain in the datasheet as 15 and each transistor with 1.125A of maximum current so the base current is 75mA. Could I use a single PNP transistor to manage all four tip35s or do I have to use one PNP transistor for each tip35? Attached is the circuit that I had planned to do.
I thank you for your collaboration and other recommendations.

 

[audioguru]

The current gain hFE on a datasheet is used when a transistor is used as a linear amplifier with plenty of emitter-collector voltage.
A transistor used as a switch (like you are doing) must saturate and the datasheet says then its base current must be 1/10th its collector current.
Then the total base current must be 0.45A and the base current of the 2n4403 must be 45mA. One 2N4403 will be fine.
re-calculate the 10 ohm resistor value.
Can your signal source produce 45mA?
Why not use a logic level Mosfet?

 

[Fercho7]

The current gain hFE on a datasheet is used when a transistor is used as a linear amplifier with plenty of emitter-collector voltage.
A transistor used as a switch (like you are doing) must saturate and the datasheet says then its base current must be 1/10th its collector current.
Then the total base current must be 0.45A and the base current of the 2n4403 must be 45mA. One 2N4403 will be fine.
re-calculate the 10 ohm resistor value.
Can your signal source produce 45mA?
Why not use a logic level Mosfet?

thanks for your reply.
Where can I find this 1/10 ratio on the datasheet, does it have a particular name? or is it a condition for all transistors in saturation?
Actually my signal source does not produce 45mA, it is an arduino, I made my assumption with 50 hfe on the 2N4403, I did not know the 1/10 ratio.
About the logic level mosfet, I hadn't thought about that, what is a good reference?
In the past, I used a traditional mosfet, the irf540. I put four irf540s in parallel and activated them with an ir2110 and 12v, the circuit worked fine with a small motor and with less voltage, but at 90v the circuit stopped working. So since the tip35c worked for me in the pretest, I stopped researching the mosfets.

 

[audioguru]

The datasheet of all transistors say its saturation specs.
An IRF540 needs a 10V gate-source voltage to fully turn on.
An IRL540 (see the "L"?) is "logic level" and needs a Vgs of 5V to fully turn on.

A transistor or Mosfet gets too hot if it has high supply voltage and high load current but it is only partially turned on.

 

[crutschow]

Where can I find this 1/10 ratio on the datasheet, does it have a particular name? or is it a condition for all transistors in saturation?

It's a condition to achieve transistor saturation.
See clip from datasheet below:
Notice that the base current is 1/10 of the collector current to assure good saturation.

 

[Fercho7]

Then the total base current must be 0.45A and the base current of the 2n4403 must be 45mA. One 2N4403 will be fine.
re-calculate the 10 ohm resistor value.
Can your signal source produce 45mA?

It's a condition to achieve transistor saturation.
See clip from datasheet below:
Notice that the base current is 1/10 of the collector current to assure good saturation.

@audioguru @crutschow Thank you very much for your help

I have planned this circuit with the tip35 and resistance values that I can easily find or complete in the store. I added a 2n2222 to handle the approximate 45mA in the base current of the 2n4403. Do you think this circuit is correct? o How can I improve it?

 

[gophert]

The TIP35C can handle 25Amps (40 peak). Why are you adding the complexity?
Make sure you use a TIP35C, the A and B versions cannot handle the 90v supply you plan to use for your motor.