My transistor is heating up very much and become failure

[Chinmaybastia]

please help me to reduce the transistor temp..

 

[bertus]

Hello,

What current has the relais when activated?
Usualy the base current is 1/10 of the collector current in a switching application.
It could well be that the 1K base resistor is to large.

Bertus

 

[Chinmaybastia]

Hello,

What current has the relais when activated?
Usualy the base current is 1/10 of the collector current in a switching application.
It could well be that the 1K base resistor is to large.

Bertus

Relay is not activating at all instead transistor got failure in few minutes just after applying the source voltage.

 

[bertus]

Hello,

Do you have a datasheet of the relais?
What is the type number of the relais?

Bertus

 

[Chinmaybastia]

Hello,

Do you have a datasheet of the relais?
What is the type number of the relais?

Bertus

 

[bertus]

Hello,

Did you try to turn over the coil contacts of the relais?
Perhaps it has a diode build in.

Bertus

 

[danadak]

What coil R do you measure with a DVM ?

The 2219 is rated for 600 mA, and has a sat V of 1V at .5A.

If you relay needed that much coil current the 2219 should have ~ 50 mA of
base drive which is totally beyond capability of 741 OpAmp which I limited
to a typical 25 mA short circuit current rating.


Regards, Dana.

 

[bertus]

Hello,

Looking at the crossreference kt603, it draws 30 mA at 12 Volts.
The transistor should have no problem with that 30 mA.

Bertus

 

[Bluejets]

please help me to reduce the transistor temp..

Obviously something a-up.(as in #6)
Show a clear photo of your connections.

 

[Harald Kapp]

The output of the 741 opamp can not reach down to 0 V. The datasheet states that the minimum output voltage is V_{out_min} = V_-+2 V (-13 V with -15 V supply, see screenshot below).

In your circuit V_- = 0 V which means V_{out_min} = 2 V.
This in turn will drive a base current of I_B = (2 V -0.6 V)/ 1 kΩ = 1.4 mA into the base of the transistor. The transistor will partially turn on. Due to being turned on only partially, not fully, the transistor will dissipate a lot of energy in the form of heat.

What you can do:

1. use a negative supply voltage of ~ -2 V... -3 V (-3.3 V can easily be created with an integrated charge pump ic) for the 741.
2. use an opamp with rail-to-rail output which can really deliver ~ 0 V when off.
3. the imho best solution: instead of abusing the 741 as a comparator, use a true comparator ic.

Addendum:
The feedback by the 100 k resistor around the 741 is not connected correctly. Assuming you want the opamp to operate as a comparator, which is the only meaningful thing I can imagine for this circuit, the feedback needs to go to the "+" input of the opamp to create a hysteresis. See e.g. here.