# simple H bridge design using power transistor

i am designing a simple h-bridge. I am using tip41 npn power transistor and 2N2955 PNP transistor in the circuit, as you can see in the attached diagram...

as we know h-bridge are basically used for controlling the direction polarity of a motor.. So my question is,

as i am using a tip41 power transistor and its collector-emitter maximum voltage is 40V, collector-base voltage is also 40V and max. collector current is 6A.

and 2N2955 whose collector-emitter maximum voltage is 60V, collector-base voltage is also 100V and max. collector current is 7A.

so of what maximum rating of motor we can control using these rating of transistors? and please have a look on my circuit diagram is it need any changes..

Also, do we need safety for the transistor from voltage spikes?

Okay first thing first, the combination of using TIP41 for npn transistor and 2N2955 for pnp is not a good ideal si,ce they are not complementary to each other. A pair of TIP120 and TIP125 will work better.

You have directly sorted the base of two transistors to your logic pins which is wrong. You should use a base resistor to limit the base current and since you are using two different transistors make sure you select the correct value of resistor for each type. Also you should make the transistor fully saturated, because only then the rated collector current will flow through it. I will not be able to answer how much voltage and current these transistor can hold until you decide the base resistor values.

Regarding the diode yes, you should use a  it to suppress voltage spikes.

Another thing to keep in mind is that power transistor will have relatively a larger base current and since we are controlling two transistors make sure your logic pin can source it.And consider the peak current of the motor as well, the collector current should be 125% of the peak current of the motor for safe operation.

Joined August 16, 2016      998
Tuesday at 12:29 AM

ok i will use TIP120 and TIP125...

but as you have said that tip41 is not complementary with 2N2955... so we can also use one which is complementary with TIP41..

or if i use TIP120 and TIP125, what is the maximum rating of the motor we can control with these two....  and how to calculate the value of base resistor?

Joined September 18, 2018      4
Tuesday at 05:38 PM